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  • TFS API Change WorkItem CreatedDate And ChangedDate To Historic Dates

    - by Tarun Arora
    There may be times when you need to modify the value of the fields “System.CreatedDate” and “System.ChangedDate” on a work item. Richard Hundhausen has a great blog with ample of reason why or why not you should need to set the values of these fields to historic dates. In this blog post I’ll show you, Create a PBI WorkItem linked to a Task work item by pre-setting the value of the field ‘System.ChangedDate’ to a historic date Change the value of the field ‘System.Created’ to a historic date Simulate the historic burn down of a task type work item in a sprint Explain the impact of updating values of the fields CreatedDate and ChangedDate on the Sprint burn down chart Rules of Play      1. You need to be a member of the Project Collection Service Accounts              2. You need to use ‘WorkItemStoreFlags.BypassRules’ when you instantiate the WorkItemStore service // Instanciate Work Item Store with the ByPassRules flag _wis = new WorkItemStore(_tfs, WorkItemStoreFlags.BypassRules);      3. You cannot set the ChangedDate         - Less than the changed date of previous revision         - Greater than current date Walkthrough The walkthrough contains 5 parts 00 – Required References 01 – Connect to TFS Programmatically 02 – Create a Work Item Programmatically 03 – Set the values of fields ‘System.ChangedDate’ and ‘System.CreatedDate’ to historic dates 04 – Results of our experiment Lets get started………………………………………………… 00 – Required References Microsoft.TeamFoundation.dll Microsoft.TeamFoundation.Client.dll Microsoft.TeamFoundation.Common.dll Microsoft.TeamFoundation.WorkItemTracking.Client.dll 01 – Connect to TFS Programmatically I have a in depth blog post on how to connect to TFS programmatically in case you are interested. However, the code snippet below will enable you to connect to TFS using the Team Project Picker. // Services I need access to globally private static TfsTeamProjectCollection _tfs; private static ProjectInfo _selectedTeamProject; private static WorkItemStore _wis; // Connect to TFS Using Team Project Picker public static bool ConnectToTfs() { var isSelected = false; // The user is allowed to select only one project var tfsPp = new TeamProjectPicker(TeamProjectPickerMode.SingleProject, false); tfsPp.ShowDialog(); // The TFS project collection _tfs = tfsPp.SelectedTeamProjectCollection; if (tfsPp.SelectedProjects.Any()) { // The selected Team Project _selectedTeamProject = tfsPp.SelectedProjects[0]; isSelected = true; } return isSelected; } 02 – Create a Work Item Programmatically In the below code snippet I have create a Product Backlog Item and a Task type work item and then link them together as parent and child. Note – You will have to set the ChangedDate to a historic date when you created the work item. Remember, If you try and set the ChangedDate to a value earlier than last assigned you will receive the following exception… TF26212: Team Foundation Server could not save your changes. There may be problems with the work item type definition. Try again or contact your Team Foundation Server administrator. If you notice below I have added a few seconds each time I have modified the ‘ChangedDate’ just to avoid running into the exception listed above. // Create Linked Work Items and return Ids private static List<int> CreateWorkItemsProgrammatically() { // Instantiate Work Item Store with the ByPassRules flag _wis = new WorkItemStore(_tfs, WorkItemStoreFlags.BypassRules); // List of work items to return var listOfWorkItems = new List<int>(); // Create a new Product Backlog Item var p = new WorkItem(_wis.Projects[_selectedTeamProject.Name].WorkItemTypes["Product Backlog Item"]); p.Title = "This is a new PBI"; p.Description = "Description"; p.IterationPath = string.Format("{0}\\Release 1\\Sprint 1", _selectedTeamProject.Name); p.AreaPath = _selectedTeamProject.Name; p["Effort"] = 10; // Just double checking that ByPassRules is set to true if (_wis.BypassRules) { p.Fields["System.ChangedDate"].Value = Convert.ToDateTime("2012-01-01"); } if (p.Validate().Count == 0) { p.Save(); listOfWorkItems.Add(p.Id); } else { Console.WriteLine(">> Following exception(s) encountered during work item save: "); foreach (var e in p.Validate()) { Console.WriteLine(" - '{0}' ", e); } } var t = new WorkItem(_wis.Projects[_selectedTeamProject.Name].WorkItemTypes["Task"]); t.Title = "This is a task"; t.Description = "Task Description"; t.IterationPath = string.Format("{0}\\Release 1\\Sprint 1", _selectedTeamProject.Name); t.AreaPath = _selectedTeamProject.Name; t["Remaining Work"] = 10; if (_wis.BypassRules) { t.Fields["System.ChangedDate"].Value = Convert.ToDateTime("2012-01-01"); } if (t.Validate().Count == 0) { t.Save(); listOfWorkItems.Add(t.Id); } else { Console.WriteLine(">> Following exception(s) encountered during work item save: "); foreach (var e in t.Validate()) { Console.WriteLine(" - '{0}' ", e); } } var linkTypEnd = _wis.WorkItemLinkTypes.LinkTypeEnds["Child"]; p.Links.Add(new WorkItemLink(linkTypEnd, t.Id) {ChangedDate = Convert.ToDateTime("2012-01-01").AddSeconds(20)}); if (_wis.BypassRules) { p.Fields["System.ChangedDate"].Value = Convert.ToDateTime("2012-01-01").AddSeconds(20); } if (p.Validate().Count == 0) { p.Save(); } else { Console.WriteLine(">> Following exception(s) encountered during work item save: "); foreach (var e in p.Validate()) { Console.WriteLine(" - '{0}' ", e); } } return listOfWorkItems; } 03 – Set the value of “Created Date” and Change the value of “Changed Date” to Historic Dates The CreatedDate can only be changed after a work item has been created. If you try and set the CreatedDate to a historic date at the time of creation of a work item, it will not work. // Lets do a work item effort burn down simulation by updating the ChangedDate & CreatedDate to historic Values private static void WorkItemChangeSimulation(IEnumerable<int> listOfWorkItems) { foreach (var id in listOfWorkItems) { var wi = _wis.GetWorkItem(id); switch (wi.Type.Name) { case "ProductBacklogItem": if (wi.State.ToLower() == "new") wi.State = "Approved"; // Advance the changed date by few seconds wi.Fields["System.ChangedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(10); // Set the CreatedDate to Changed Date wi.Fields["System.CreatedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(10); wi.Save(); break; case "Task": // Advance the changed date by few seconds wi.Fields["System.ChangedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(10); // Set the CreatedDate to Changed date wi.Fields["System.CreatedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(10); wi.Save(); break; } } // A mock sprint start date var sprintStart = DateTime.Today.AddDays(-5); // A mock sprint end date var sprintEnd = DateTime.Today.AddDays(5); // What is the total Sprint duration var totalSprintDuration = (sprintEnd - sprintStart).Days; // How much of the sprint have we already covered var noOfDaysIntoSprint = (DateTime.Today - sprintStart).Days; // Get the effort assigned to our tasks var totalEffortRemaining = QueryTaskTotalEfforRemaining(listOfWorkItems); // Defining how much effort to burn every day decimal dailyBurnRate = totalEffortRemaining / totalSprintDuration < 1 ? 1 : totalEffortRemaining / totalSprintDuration; // we have just created one task var totalNoOfTasks = 1; var simulation = sprintStart; var currentDate = DateTime.Today.Date; // Carry on till effort has been burned down from sprint start to today while (simulation.Date != currentDate.Date) { var dailyBurnRate1 = dailyBurnRate; // A fixed amount needs to be burned down each day while (dailyBurnRate1 > 0) { // burn down bit by bit from all unfinished task type work items foreach (var id in listOfWorkItems) { var wi = _wis.GetWorkItem(id); var isDirty = false; // Set the status to in progress if (wi.State.ToLower() == "to do") { wi.State = "In Progress"; isDirty = true; } // Ensure that there is enough effort remaining in tasks to burn down the daily burn rate if (QueryTaskTotalEfforRemaining(listOfWorkItems) > dailyBurnRate1) { // If there is less than 1 unit of effort left in the task, burn it all if (Convert.ToDecimal(wi["Remaining Work"]) <= 1) { wi["Remaining Work"] = 0; dailyBurnRate1 = dailyBurnRate1 - Convert.ToDecimal(wi["Remaining Work"]); isDirty = true; } else { // How much to burn from each task? var toBurn = (dailyBurnRate / totalNoOfTasks) < 1 ? 1 : (dailyBurnRate / totalNoOfTasks); // Check that the task has enough effort to allow burnForTask effort if (Convert.ToDecimal(wi["Remaining Work"]) >= toBurn) { wi["Remaining Work"] = Convert.ToDecimal(wi["Remaining Work"]) - toBurn; dailyBurnRate1 = dailyBurnRate1 - toBurn; isDirty = true; } else { wi["Remaining Work"] = 0; dailyBurnRate1 = dailyBurnRate1 - Convert.ToDecimal(wi["Remaining Work"]); isDirty = true; } } } else { dailyBurnRate1 = 0; } if (isDirty) { if (Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).Date == simulation.Date) { wi.Fields["System.ChangedDate"].Value = Convert.ToDateTime(wi.Fields["System.ChangedDate"].Value).AddSeconds(20); } else { wi.Fields["System.ChangedDate"].Value = simulation.AddSeconds(20); } wi.Save(); } } } // Increase date by 1 to perform daily burn down by day simulation = Convert.ToDateTime(simulation).AddDays(1); } } // Get the Total effort remaining in the current sprint private static decimal QueryTaskTotalEfforRemaining(List<int> listOfWorkItems) { var unfinishedWorkInCurrentSprint = _wis.GetQueryDefinition( new Guid(QueryAndGuid.FirstOrDefault(c => c.Key == "Unfinished Work").Value)); var parameters = new Dictionary<string, object> { { "project", _selectedTeamProject.Name } }; var q = new Query(_wis, unfinishedWorkInCurrentSprint.QueryText, parameters); var results = q.RunLinkQuery(); var wis = new List<WorkItem>(); foreach (var result in results) { var _wi = _wis.GetWorkItem(result.TargetId); if (_wi.Type.Name == "Task" && listOfWorkItems.Contains(_wi.Id)) wis.Add(_wi); } return wis.Sum(r => Convert.ToDecimal(r["Remaining Work"])); }   04 – The Results If you are still reading, the results are beautiful! Image 1 – Create work item with Changed Date pre-set to historic date Image 2 – Set the CreatedDate to historic date (Same as the ChangedDate) Image 3 – Simulate of effort burn down on a task via the TFS API   Image 4 – The history of changes on the Task. So, essentially this task has burned 1 hour per day Sprint Burn Down Chart – What’s not possible? The Sprint burn down chart is calculated from the System.AuthorizedDate and not the System.ChangedDate/System.CreatedDate. So, though you can change the System.ChangedDate and System.CreatedDate to historic dates you will not be able to synthesize the sprint burn down chart. Image 1 – By changing the Created Date and Changed Date to ‘18/Oct/2012’ you would have expected the burn down to have been impacted, but it won’t be, because the sprint burn down chart uses the value of field ‘System.AuthorizedDate’ to calculate the unfinished work points. The AsOf queries that are used to calculate the unfinished work points use the value of the field ‘System.AuthorizedDate’. Image 2 – Using the above code I burned down 1 hour effort per day over 5 days from the task work item, I would have expected the sprint burn down to show a constant burn down, instead the burn down shows the effort exhausted on the 24th itself. Simply because the burn down is calculated using the ‘System.AuthorizedDate’. Now you would ask… “Can I change the value of the field System.AuthorizedDate to a historic date” Unfortunately that’s not possible! You will run into the exception ValidationException –  “TF26194: The value for field ‘Authorized Date’ cannot be changed.” Conclusion - You need to be a member of the Project Collection Service account group in order to set the fields ‘System.ChangedDate’ and ‘System.CreatedDate’ to historic dates - You need to instantiate the WorkItemStore using the flag ByPassValidation - The System.ChangedDate needs to be set to a historic date at the time of work item creation. You cannot reset the ChangedDate to a date earlier than the existing ChangedDate and you cannot reset the ChangedDate to a date greater than the current date time. - The System.CreatedDate can only be reset after a work item has been created. You cannot set the CreatedDate at the time of work item creation. The CreatedDate cannot be greater than the current date. You can however reset the CreatedDate to a date earlier than the existing value. - You will not be able to synthesize the Sprint burn down chart by changing the value of System.ChangedDate and System.CreatedDate to historic dates, since the burn down chart uses AsOf queries to calculate the unfinished work points which internally uses the System.AuthorizedDate and NOT the System.ChangedDate & System.CreatedDate - System.AuthorizedDate cannot be set to a historic date using the TFS API Read other posts on using the TFS API here… Enjoy!

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  • What Keeps You from Changing Your Public IP Address and Wreaking Havoc on the Internet?

    - by Jason Fitzpatrick
    What exactly is preventing you (or anyone else) from changing their IP address and causing all sorts of headaches for ISPs and other Internet users? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. The Question SuperUser reader Whitemage is curious about what’s preventing him from wantonly changing his IP address and causing trouble: An interesting question was asked of me and I did not know what to answer. So I’ll ask here. Let’s say I subscribed to an ISP and I’m using cable internet access. The ISP gives me a public IP address of 60.61.62.63. What keeps me from changing this IP address to, let’s say, 60.61.62.75, and messing with another consumer’s internet access? For the sake of this argument, let’s say that this other IP address is also owned by the same ISP. Also, let’s assume that it’s possible for me to go into the cable modem settings and manually change the IP address. Under a business contract where you are allocated static addresses, you are also assigned a default gateway, a network address and a broadcast address. So that’s 3 addresses the ISP “loses” to you. That seems very wasteful for dynamically assigned IP addresses, which the majority of customers are. Could they simply be using static arps? ACLs? Other simple mechanisms? Two things to investigate here, why can’t we just go around changing our addresses, and is the assignment process as wasteful as it seems? The Answer SuperUser contributor Moses offers some insight: Cable modems aren’t like your home router (ie. they don’t have a web interface with simple point-and-click buttons that any kid can “hack” into). Cable modems are “looked up” and located by their MAC address by the ISP, and are typically accessed by technicians using proprietary software that only they have access to, that only runs on their servers, and therefore can’t really be stolen. Cable modems also authenticate and cross-check settings with the ISPs servers. The server has to tell the modem whether it’s settings (and location on the cable network) are valid, and simply sets it to what the ISP has it set it for (bandwidth, DHCP allocations, etc). For instance, when you tell your ISP “I would like a static IP, please.”, they allocate one to the modem through their servers, and the modem allows you to use that IP. Same with bandwidth changes, for instance. To do what you are suggesting, you would likely have to break into the servers at the ISP and change what it has set up for your modem. Could they simply be using static arps? ACLs? Other simple mechanisms? Every ISP is different, both in practice and how close they are with the larger network that is providing service to them. Depending on those factors, they could be using a combination of ACL and static ARP. It also depends on the technology in the cable network itself. The ISP I worked for used some form of ACL, but that knowledge was a little beyond my paygrade. I only got to work with the technician’s interface and do routine maintenance and service changes. What keeps me from changing this IP address to, let’s say, 60.61.62.75 and mess with another consumer’s internet access? Given the above, what keeps you from changing your IP to one that your ISP hasn’t specifically given to you is a server that is instructing your modem what it can and can’t do. Even if you somehow broke into the modem, if 60.61.62.75 is already allocated to another customer, then the server will simply tell your modem that it can’t have it. David Schwartz offers some additional insight with a link to a white paper for the really curious: Most modern ISPs (last 13 years or so) will not accept traffic from a customer connection with a source IP address they would not route to that customer were it the destination IP address. This is called “reverse path forwarding”. See BCP 38. Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.     

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  • [Windows 8] An application bar toggle button

    - by Benjamin Roux
    To stay in the application bar stuff, here’s another useful control which enable to create an application bar button that can be toggled between two different contents/styles/commands (used to create a favorite/unfavorite or a play/pause button for example). namespace Indeed.Controls { public class AppBarToggleButton : Button { public bool IsChecked { get { return (bool)GetValue(IsCheckedProperty); } set { SetValue(IsCheckedProperty, value); } } public static readonly DependencyProperty IsCheckedProperty = DependencyProperty.Register("IsChecked", typeof(bool), typeof(AppBarToggleButton), new PropertyMetadata(false, (o, e) => (o as AppBarToggleButton).IsCheckedChanged())); public string CheckedContent { get { return (string)GetValue(CheckedContentProperty); } set { SetValue(CheckedContentProperty, value); } } public static readonly DependencyProperty CheckedContentProperty = DependencyProperty.Register("CheckedContent", typeof(string), typeof(AppBarToggleButton), null); public ICommand CheckedCommand { get { return (ICommand)GetValue(CheckedCommandProperty); } set { SetValue(CheckedCommandProperty, value); } } public static readonly DependencyProperty CheckedCommandProperty = DependencyProperty.Register("CheckedCommand", typeof(ICommand), typeof(AppBarToggleButton), null); public Style CheckedStyle { get { return (Style)GetValue(CheckedStyleProperty); } set { SetValue(CheckedStyleProperty, value); } } public static readonly DependencyProperty CheckedStyleProperty = DependencyProperty.Register("CheckedStyle", typeof(Style), typeof(AppBarToggleButton), null); public bool AutoToggle { get { return (bool)GetValue(AutoToggleProperty); } set { SetValue(AutoToggleProperty, value); } } public static readonly DependencyProperty AutoToggleProperty = DependencyProperty.Register("AutoToggle", typeof(bool), typeof(AppBarToggleButton), null); private object content; private ICommand command; private Style style; private void IsCheckedChanged() { if (IsChecked) { // backup the current content and command content = Content; command = Command; style = Style; if (CheckedStyle == null) Content = CheckedContent; else Style = CheckedStyle; Command = CheckedCommand; } else { if (CheckedStyle == null) Content = content; else Style = style; Command = command; } } protected override void OnTapped(Windows.UI.Xaml.Input.TappedRoutedEventArgs e) { base.OnTapped(e); if (AutoToggle) IsChecked = !IsChecked; } } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } To use it, it’s very simple. <ic:AppBarToggleButton Style="{StaticResource PlayAppBarButtonStyle}" CheckedStyle="{StaticResource PauseAppBarButtonStyle}" Command="{Binding Path=PlayCommand}" CheckedCommand="{Binding Path=PauseCommand}" IsChecked="{Binding Path=IsPlaying}" /> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } When the IsPlaying property (in my ViewModel) is true the button becomes a Pause button, when it’s false it becomes a Play button. Warning: Just make sure that the IsChecked property is set in last in your control !! If you don’t use style you can alternatively use Content and CheckedContent. Furthermore you can set the AutoToggle to true if you don’t want to control is IsChecked property through binding. With this control and the AppBarPopupButton, you can now create awesome application bar for your apps ! Stay tuned for more awesome Windows 8 tricks !

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  • Opposite Force to Apply to a Collided Rigid Body?

    - by Milo
    I'm working on the physics for my GTA2-like game so I can learn more about game physics. The collision detection and resolution are working great. I'm now just unsure how to compute the force to apply to a body after it collides with a wall. My rigid body looks like this: /our simulation object class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; private Vector2D v = new Vector2D(); //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; private Matrix mat = new Matrix(); private float[] Vector2Ds = new float[2]; private Vector2D tangent = new Vector2D(); private static Vector2D worldRelVec = new Vector2D(); private static Vector2D relWorldVec = new Vector2D(); private static Vector2D pointVelVec = new Vector2D(); private static Vector2D acceleration = new Vector2D(); public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; setLayer(LAYER_OBJECTS); } protected void rectChanged() { if(getWorld() != null) { getWorld().updateDynamic(this); } } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position.x,position.y, getWidth(), getHeight(), angle); rectChanged(); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { doUpdate(timeStep); } public void doUpdate(float timeStep) { //integrate physics //linear acceleration.x = forces.x / mass; acceleration.y = forces.y / mass; velocity.x += (acceleration.x * timeStep); velocity.y += (acceleration.y * timeStep); //velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); v.x = getRect().getCenter().getX() + (velocity.x * timeStep); v.y = getRect().getCenter().getY() + (velocity.y * timeStep); setCenter(v.x, v.y); forces.x = 0; //clear forces forces.y = 0; //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { mat.reset(); Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); relWorldVec.x = Vector2Ds[0]; relWorldVec.y = Vector2Ds[1]; return relWorldVec; } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { mat.reset(); Vector2Ds[0] = world.x; Vector2Ds[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vector2Ds); worldRelVec.x = Vector2Ds[0]; worldRelVec.y = Vector2Ds[1]; return worldRelVec; } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { tangent.x = -worldOffset.y; tangent.y = worldOffset.x; pointVelVec.x = (tangent.x * angularVelocity) + velocity.x; pointVelVec.y = (tangent.y * angularVelocity) + velocity.y; return pointVelVec; } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces.x += worldForce.x; forces.y += worldForce.y; //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } public Vector2D getVelocity() { return velocity; } public void setVelocity(Vector2D velocity) { this.velocity = velocity; } } The way it is given force is by the applyForce method, this method considers angular torque. I'm just not sure how to come up with the vectors in the case where: RigidBody hits static entity RigidBody hits other RigidBody that may or may not be in motion. Would anyone know a way (without too complex math) that I could figure out the opposite force I need to apply to the car? I know the normal it is colliding with and how deep it collided. My main goal is so that say I hit a building from the side, well the car should not just stay there, it should slowly rotate out of it if I'm more than 45 degrees. Right now when I hit a wall I only change the velocity directly which does not consider angular force. Thanks!

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  • await, WhenAll, WaitAll, oh my!!

    - by cibrax
    If you are dealing with asynchronous work in .NET, you might know that the Task class has become the main driver for wrapping asynchronous calls. Although this class was officially introduced in .NET 4.0, the programming model for consuming tasks was much more simplified in C# 5.0 in .NET 4.5 with the addition of the new async/await keywords. In a nutshell, you can use these keywords to make asynchronous calls as if they were sequential, and avoiding in that way any fork or callback in the code. The compiler takes care of the rest. I was yesterday writing some code for making multiple asynchronous calls to backend services in parallel. The code looked as follow, var allResults = new List<Result>(); foreach(var provider in providers) { var results = await provider.GetResults(); allResults.AddRange(results); } return allResults; You see, I was using the await keyword to make multiple calls in parallel. Something I did not consider was the overhead this code implied after being compiled. I started an interesting discussion with some smart folks in twitter. One of them, Tugberk Ugurlu, had the brilliant idea of actually write some code to make a performance comparison with another approach using Task.WhenAll. There are two additional methods you can use to wait for the results of multiple calls in parallel, WhenAll and WaitAll. WhenAll creates a new task and waits for results in that new task, so it does not block the calling thread. WaitAll, on the other hand, blocks the calling thread. This is the code Tugberk initially wrote, and I modified afterwards to also show the results of WaitAll. class Program { private static Func<Stopwatch, Task>[] funcs = new Func<Stopwatch, Task>[] { async (watch) => { watch.Start(); await Task.Delay(1000); Console.WriteLine("1000 one has been completed."); }, async (watch) => { await Task.Delay(1500); Console.WriteLine("1500 one has been completed."); }, async (watch) => { await Task.Delay(2000); Console.WriteLine("2000 one has been completed."); watch.Stop(); Console.WriteLine(watch.ElapsedMilliseconds + "ms has been elapsed."); } }; static void Main(string[] args) { Console.WriteLine("Await in loop work starts..."); DoWorkAsync().ContinueWith(task => { Console.WriteLine("Parallel work starts..."); DoWorkInParallelAsync().ContinueWith(t => { Console.WriteLine("WaitAll work starts..."); WaitForAll(); }); }); Console.ReadLine(); } static async Task DoWorkAsync() { Stopwatch watch = new Stopwatch(); foreach (var func in funcs) { await func(watch); } } static async Task DoWorkInParallelAsync() { Stopwatch watch = new Stopwatch(); await Task.WhenAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } static void WaitForAll() { Stopwatch watch = new Stopwatch(); Task.WaitAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } } After running this code, the results were very concluding. Await in loop work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 4532ms has been elapsed. Parallel work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2007ms has been elapsed. WaitAll work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2009ms has been elapsed. The await keyword in a loop does not really make the calls in parallel.

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  • Example: Controlling randomizer using code contracts

    - by DigiMortal
    One cool addition to Visual Studio 2010 is support for code contracts. Code contracts make sure that all conditions under what method is supposed to run correctly are met. Those who are familiar with unit tests will find code contracts easy to use. In this posting I will show you simple example about static contract checking (example solution is included). To try out code contracts you need at least Visual Studio 2010 Standard Edition. Also you need code contracts package. You can download package from DevLabs Code Contracts page. NB! Speakers, you can use the example solution in your presentations as long as you mention me and this blog in your sessions. Solution has readme.txt file that gives you steps to go through when presenting solution in sessions. This blog posting is companion posting for Visual Studio solution referred below. As an example let’s look at the following class. public class Randomizer {     public static int GetRandomFromRange(int min, int max)     {         var rnd = new Random();         return rnd.Next(min, max);     }       public static int GetRandomFromRangeContracted(int min, int max)     {         Contract.Requires(min < max, "Min must be less than max");           var rnd = new Random();         return rnd.Next(min, max);     } } GetRandomFromRange() method returns results without any checking. GetRandomFromRangeContracted() uses one code contract that makes sure that minimum value is less than maximum value. Now let’s run the following code. class Program {     static void Main(string[] args)     {         var random1 = Randomizer.GetRandomFromRange(0, 9);         Console.WriteLine("Random 1: " + random1);           var random2 = Randomizer.GetRandomFromRange(1, 1);         Console.WriteLine("Random 2: " + random2);           var random3 = Randomizer.GetRandomFromRangeContracted(5, 5);         Console.WriteLine("Random 3: " + random3);           Console.WriteLine(" ");         Console.WriteLine("Press any key to exit ...");         Console.ReadKey();     } } As we have not turned on support for code contracts the code runs without any problems and we get no warnings by Visual Studio that something is wrong. Now let’s turn on static checking for code contracts. As you can see then code still compiles without any errors but Visual Studio warns you about possible problems with contracts. Click on image to see it at original size.  When we open Error list and run our application we get the following output to errors list. Note that these messages are not shown immediately. There is little delay between application starting and appearance of these messages. So wait couple of seconds before going out of your mind. Click on image to see it at original size.  If you look at these warnings you can see that warnings show you illegal calls and also contracts against what they are going. Third warning points to GetRandomFromRange() method and shows that there should be also problem that can be detected by contract. Download Code Contracts example VS2010 solution | 30KB

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  • Thread.Interrupt Is Evil

    - by Alois Kraus
    Recently I have found an interesting issue with Thread.Interrupt during application shutdown. Some application was crashing once a week and we had not really a clue what was the issue. Since it happened not very often it was left as is until we have got some memory dumps during the crash. A memory dump usually means WindDbg which I really like to use (I know I am one of the very few fans of it).  After a quick analysis I did find that the main thread already had exited and the thread with the crash was stuck in a Monitor.Wait. Strange Indeed. Running the application a few thousand times under the debugger would potentially not have shown me what the reason was so I decided to what I call constructive debugging. I did create a simple Console application project and try to simulate the exact circumstances when the crash did happen from the information I have via memory dump and source code reading. The thread that was  crashing was actually MS code from an old version of the Microsoft Caching Application Block. From reading the code I could conclude that the main thread did call the Dispose method on the CacheManger class which did call Thread.Interrupt on the cache scavenger thread which was just waiting for work to do. My first version of the repro looked like this   static void Main(string[] args) { Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); } static void ThreadFunc() { while (true) { object value = Dequeue(); // block until unblocked or awaken via ThreadInterruptedException } } static object WaitObject = new object(); static object Dequeue() { object lret = "got value"; try { lock (WaitObject) { } } catch (ThreadInterruptedException) { Console.WriteLine("Got ThreadInterruptException"); lret = null; } return lret; } I do start a background thread and call Thread.Interrupt on it and then directly let the application terminate. The thread in the meantime does plenty of Monitor.Enter/Leave calls to simulate work on it. This first version did not crash. So I need to dig deeper. From the memory dump I did know that the finalizer thread was doing just some critical finalizers which were closing file handles. Ok lets add some long running finalizers to the sample. class FinalizableObject : CriticalFinalizerObject { ~FinalizableObject() { Console.WriteLine("Hi we are waiting to finalize now and block the finalizer thread for 5s."); Thread.Sleep(5000); } } class Program { static void Main(string[] args) { FinalizableObject fin = new FinalizableObject(); Thread t = new Thread(ThreadFunc) { IsBackground = true, Name = "Test Thread" }; t.Start(); Console.WriteLine("Interrupt Thread"); t.Interrupt(); GC.KeepAlive(fin); // prevent finalizing it too early // After leaving main the other thread is woken up via Thread.Abort // while we are finalizing. This causes a stackoverflow in the CLR ThreadAbortException handling at this time. } With this changed Main method and a blocking critical finalizer I did get my crash just like the real application. The funny thing is that this is actually a CLR bug. When the main method is left the CLR does suspend all threads except the finalizer thread and declares all objects as garbage. After the normal finalizers were called the critical finalizers are executed to e.g. free OS handles (usually). Remember that I did call Thread.Interrupt as one of the last methods in the Main method. The Interrupt method is actually asynchronous and does wake a thread up and throws a ThreadInterruptedException only once unlike Thread.Abort which does rethrow the exception when an exception handling clause is left. It seems that the CLR does not expect that a frozen thread does wake up again while the critical finalizers are executed. While trying to raise a ThreadInterrupedException the CLR goes down with an stack overflow. Ups not so nice. Why has this nobody noticed for years is my next question. As it turned out this error does only happen on the CLR for .NET 4.0 (x86 and x64). It does not show up in earlier or later versions of the CLR. I have reported this issue on connect here but so far it was not confirmed as a CLR bug. But I would be surprised if my console application was to blame for a stack overflow in my test thread in a Monitor.Wait call. What is the moral of this story? Thread.Abort is evil but Thread.Interrupt is too. It is so evil that even the CLR of .NET 4.0 contains a race condition during the CLR shutdown. When the CLR gurus can get it wrong the chances are high that you get it wrong too when you use this constructs. If you do not believe me see what Patrick Smacchia does blog about Thread.Abort and List.Sort. Not only the CLR creators can get it wrong. The BCL writers do sometimes have a hard time with correct exception handling as well. If you do tell me that you use Thread.Abort frequently and never had problems with it I do suspect that you do not have looked deep enough into your application to find such sporadic errors.

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  • Inside BackgroundWorker

    - by João Angelo
    The BackgroundWorker is a reusable component that can be used in different contexts, but sometimes with unexpected results. If you are like me, you have mostly used background workers while doing Windows Forms development due to the flexibility they offer for running a background task. They support cancellation and give events that signal progress updates and task completion. When used in Windows Forms, these events (ProgressChanged and RunWorkerCompleted) get executed back on the UI thread where you can freely access your form controls. However, the logic of the progress changed and worker completed events being invoked in the thread that started the background worker is not something you get directly from the BackgroundWorker, but instead from the fact that you are running in the context of Windows Forms. Take the following example that illustrates the use of a worker in three different scenarios: – Console Application or Windows Service; – Windows Forms; – WPF. using System; using System.ComponentModel; using System.Threading; using System.Windows.Forms; using System.Windows.Threading; class Program { static AutoResetEvent Synch = new AutoResetEvent(false); static void Main() { var bw1 = new BackgroundWorker(); var bw2 = new BackgroundWorker(); var bw3 = new BackgroundWorker(); Console.WriteLine("DEFAULT"); var unspecializedThread = new Thread(() => { OutputCaller(1); SynchronizationContext.SetSynchronizationContext( new SynchronizationContext()); bw1.DoWork += (sender, e) => OutputWork(1); bw1.RunWorkerCompleted += (sender, e) => OutputCompleted(1); // Uses default SynchronizationContext bw1.RunWorkerAsync(); }); unspecializedThread.IsBackground = true; unspecializedThread.Start(); Synch.WaitOne(); Console.WriteLine(); Console.WriteLine("WINDOWS FORMS"); var windowsFormsThread = new Thread(() => { OutputCaller(2); SynchronizationContext.SetSynchronizationContext( new WindowsFormsSynchronizationContext()); bw2.DoWork += (sender, e) => OutputWork(2); bw2.RunWorkerCompleted += (sender, e) => OutputCompleted(2); // Uses WindowsFormsSynchronizationContext bw2.RunWorkerAsync(); Application.Run(); }); windowsFormsThread.IsBackground = true; windowsFormsThread.SetApartmentState(ApartmentState.STA); windowsFormsThread.Start(); Synch.WaitOne(); Console.WriteLine(); Console.WriteLine("WPF"); var wpfThread = new Thread(() => { OutputCaller(3); SynchronizationContext.SetSynchronizationContext( new DispatcherSynchronizationContext()); bw3.DoWork += (sender, e) => OutputWork(3); bw3.RunWorkerCompleted += (sender, e) => OutputCompleted(3); // Uses DispatcherSynchronizationContext bw3.RunWorkerAsync(); Dispatcher.Run(); }); wpfThread.IsBackground = true; wpfThread.SetApartmentState(ApartmentState.STA); wpfThread.Start(); Synch.WaitOne(); } static void OutputCaller(int workerId) { Console.WriteLine( "bw{0}.{1} | Thread: {2} | IsThreadPool: {3}", workerId, "RunWorkerAsync".PadRight(18), Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread); } static void OutputWork(int workerId) { Console.WriteLine( "bw{0}.{1} | Thread: {2} | IsThreadPool: {3}", workerId, "DoWork".PadRight(18), Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread); } static void OutputCompleted(int workerId) { Console.WriteLine( "bw{0}.{1} | Thread: {2} | IsThreadPool: {3}", workerId, "RunWorkerCompleted".PadRight(18), Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.IsThreadPoolThread); Synch.Set(); } } Output: //DEFAULT //bw1.RunWorkerAsync | Thread: 3 | IsThreadPool: False //bw1.DoWork | Thread: 4 | IsThreadPool: True //bw1.RunWorkerCompleted | Thread: 5 | IsThreadPool: True //WINDOWS FORMS //bw2.RunWorkerAsync | Thread: 6 | IsThreadPool: False //bw2.DoWork | Thread: 5 | IsThreadPool: True //bw2.RunWorkerCompleted | Thread: 6 | IsThreadPool: False //WPF //bw3.RunWorkerAsync | Thread: 7 | IsThreadPool: False //bw3.DoWork | Thread: 5 | IsThreadPool: True //bw3.RunWorkerCompleted | Thread: 7 | IsThreadPool: False As you can see the output between the first and remaining scenarios is somewhat different. While in Windows Forms and WPF the worker completed event runs on the thread that called RunWorkerAsync, in the first scenario the same event runs on any thread available in the thread pool. Another scenario where you can get the first behavior, even when on Windows Forms or WPF, is if you chain the creation of background workers, that is, you create a second worker in the DoWork event handler of an already running worker. Since the DoWork executes in a thread from the pool the second worker will use the default synchronization context and the completed event will not run in the UI thread.

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  • spliiting code in java-don't know what's wrong [closed]

    - by ???? ?????
    I'm writing a code to split a file into many files with a size specified in the code, and then it will join these parts later. The problem is with the joining code, it doesn't work and I can't figure what is wrong! This is my code: import java.io.*; import java.util.*; public class StupidSplit { static final int Chunk_Size = 10; static int size =0; public static void main(String[] args) throws IOException { String file = "b.txt"; int chunks = DivideFile(file); System.out.print((new File(file)).delete()); System.out.print(JoinFile(file, chunks)); } static boolean JoinFile(String fname, int nChunks) { /* * Joins the chunks together. Chunks have been divided using DivideFile * function so the last part of filename will ".partxxxx" Checks if all * parts are together by matching number of chunks found against * "nChunks", then joins the file otherwise throws an error. */ boolean successful = false; File currentDirectory = new File(System.getProperty("user.dir")); // File[] fileList = currentDirectory.listFiles(); /* populate only the files having extension like "partxxxx" */ List<File> lst = new ArrayList<File>(); // Arrays.sort(fileList); for (File file : fileList) { if (file.isFile()) { String fnm = file.getName(); int lastDot = fnm.lastIndexOf('.'); // add to list which match the name given by "fname" and have //"partxxxx" as extension" if (fnm.substring(0, lastDot).equalsIgnoreCase(fname) && (fnm.substring(lastDot + 1)).substring(0, 4).equals("part")) { lst.add(file); } } } /* * sort the list - it will be sorted by extension only because we have * ensured that list only contains those files that have "fname" and * "part" */ File[] files = (File[]) lst.toArray(new File[0]); Arrays.sort(files); System.out.println("size ="+files.length); System.out.println("hello"); /* Ensure that number of chunks match the length of array */ if (files.length == nChunks-1) { File ofile = new File(fname); FileOutputStream fos; FileInputStream fis; byte[] fileBytes; int bytesRead = 0; try { fos = new FileOutputStream(ofile,true); for (File file : files) { fis = new FileInputStream(file); fileBytes = new byte[(int) file.length()]; bytesRead = fis.read(fileBytes, 0, (int) file.length()); assert(bytesRead == fileBytes.length); assert(bytesRead == (int) file.length()); fos.write(fileBytes); fos.flush(); fileBytes = null; fis.close(); fis = null; } fos.close(); fos = null; } catch (FileNotFoundException fnfe) { System.out.println("Could not find file"); successful = false; return successful; } catch (IOException ioe) { System.out.println("Cannot write to disk"); successful = false; return successful; } /* ensure size of file matches the size given by server */ successful = (ofile.length() == StupidSplit.size) ? true : false; } else { successful = false; } return successful; } static int DivideFile(String fname) { File ifile = new File(fname); FileInputStream fis; String newName; FileOutputStream chunk; //int fileSize = (int) ifile.length(); double fileSize = (double) ifile.length(); //int nChunks = 0, read = 0, readLength = Chunk_Size; int nChunks = 0, read = 0, readLength = Chunk_Size; byte[] byteChunk; try { fis = new FileInputStream(ifile); StupidSplit.size = (int)ifile.length(); while (fileSize > 0) { if (fileSize <= Chunk_Size) { readLength = (int) fileSize; } byteChunk = new byte[readLength]; read = fis.read(byteChunk, 0, readLength); fileSize -= read; assert(read==byteChunk.length); nChunks++; //newName = fname + ".part" + Integer.toString(nChunks - 1); newName = String.format("%s.part%09d", fname, nChunks - 1); chunk = new FileOutputStream(new File(newName)); chunk.write(byteChunk); chunk.flush(); chunk.close(); byteChunk = null; chunk = null; } fis.close(); System.out.println(nChunks); // fis = null; } catch (FileNotFoundException fnfe) { System.out.println("Could not find the given file"); System.exit(-1); } catch (IOException ioe) { System.out .println("Error while creating file chunks. Exiting program"); System.exit(-1); }System.out.println(nChunks); return nChunks; } } }

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  • Confusing Java syntax...

    - by posfan12
    I'm trying to convert the following code (from Wikipedia) from Java to JavaScript: /* * 3 June 2003, [[:en:User:Cyp]]: * Maze, generated by my algorithm * 24 October 2006, [[:en:User:quin]]: * Source edited for clarity * 25 January 2009, [[:en:User:DebateG]]: * Source edited again for clarity and reusability * 1 June 2009, [[:en:User:Nandhp]]: * Source edited to produce SVG file when run from the command-line * * This program was originally written by [[:en:User:Cyp]], who * attached it to the image description page for an image generated by * it on en.wikipedia. The image was licensed under CC-BY-SA-3.0/GFDL. */ import java.awt.*; import java.applet.*; import java.util.Random; /* Define the bit masks */ class Constants { public static final int WALL_ABOVE = 1; public static final int WALL_BELOW = 2; public static final int WALL_LEFT = 4; public static final int WALL_RIGHT = 8; public static final int QUEUED = 16; public static final int IN_MAZE = 32; } public class Maze extends java.applet.Applet { /* The width and height (in cells) of the maze */ private int width; private int height; private int maze[][]; private static final Random rnd = new Random(); /* The width in pixels of each cell */ private int cell_width; /* Construct a Maze with the default width, height, and cell_width */ public Maze() { this(20,20,10); } /* Construct a Maze with specified width, height, and cell_width */ public Maze(int width, int height, int cell_width) { this.width = width; this.height = height; this.cell_width = cell_width; } /* Initialization method that will be called when the program is * run from the command-line. Maze will be written as SVG file. */ public static void main(String[] args) { Maze m = new Maze(); m.createMaze(); m.printSVG(); } /* Initialization method that will be called when the program is * run as an applet. Maze will be displayed on-screen. */ public void init() { createMaze(); } /* The maze generation algorithm. */ private void createMaze(){ int x, y, n, d; int dx[] = { 0, 0, -1, 1 }; int dy[] = { -1, 1, 0, 0 }; int todo[] = new int[height * width], todonum = 0; /* We want to create a maze on a grid. */ maze = new int[width][height]; /* We start with a grid full of walls. */ for (x = 0; x < width; ++x) { for (y = 0; y < height; ++y) { if (x == 0 || x == width - 1 || y == 0 || y == height - 1) { maze[x][y] = Constants.IN_MAZE; } else { maze[x][y] = 63; } } } /* Select any square of the grid, to start with. */ x = 1 + rnd.nextInt (width - 2); y = 1 + rnd.nextInt (height - 2); /* Mark this square as connected to the maze. */ maze[x][y] &= ~48; /* Remember the surrounding squares, as we will */ for (d = 0; d < 4; ++d) { if ((maze[][d][][d] & Constants.QUEUED) != 0) { /* want to connect them to the maze. */ todo[todonum++] = ((x + dx[d]) << Constants.QUEUED) | (y + dy[d]); maze[][d][][d] &= ~Constants.QUEUED; } } /* We won't be finished until all is connected. */ while (todonum > 0) { /* We select one of the squares next to the maze. */ n = rnd.nextInt (todonum); x = todo[n] >> 16; /* the top 2 bytes of the data */ y = todo[n] & 65535; /* the bottom 2 bytes of the data */ /* We will connect it, so remove it from the queue. */ todo[n] = todo[--todonum]; /* Select a direction, which leads to the maze. */ do { d = rnd.nextInt (4); } while ((maze[][d][][d] & Constants.IN_MAZE) != 0); /* Connect this square to the maze. */ maze[x][y] &= ~((1 << d) | Constants.IN_MAZE); maze[][d][][d] &= ~(1 << (d ^ 1)); /* Remember the surrounding squares, which aren't */ for (d = 0; d < 4; ++d) { if ((maze[][d][][d] & Constants.QUEUED) != 0) { /* connected to the maze, and aren't yet queued to be. */ todo[todonum++] = ((x + dx[d]) << Constants.QUEUED) | (y + dy[d]); maze[][d][][d] &= ~Constants.QUEUED; } } /* Repeat until finished. */ } /* Add an entrance and exit. */ maze[1][1] &= ~Constants.WALL_ABOVE; maze[width - 2][height - 2] &= ~Constants.WALL_BELOW; } /* Called by the applet infrastructure to display the maze on-screen. */ public void paint(Graphics g) { drawMaze(g); } /* Called to write the maze to an SVG file. */ public void printSVG() { System.out.format("<svg width=\"%d\" height=\"%d\" version=\"1.1\"" + " xmlns=\"http://www.w3.org/2000/svg\">\n", width*cell_width, height*cell_width); System.out.println(" <g stroke=\"black\" stroke-width=\"1\"" + " stroke-linecap=\"round\">"); drawMaze(null); System.out.println(" </g>\n</svg>"); } /* Main maze-drawing loop. */ public void drawMaze(Graphics g) { int x, y; for (x = 1; x < width - 1; ++x) { for (y = 1; y < height - 1; ++y) { if ((maze[x][y] & Constants.WALL_ABOVE) != 0) drawLine( x * cell_width, y * cell_width, (x + 1) * cell_width, y * cell_width, g); if ((maze[x][y] & Constants.WALL_BELOW) != 0) drawLine( x * cell_width, (y + 1) * cell_width, (x + 1) * cell_width, (y + 1) * cell_width, g); if ((maze[x][y] & Constants.WALL_LEFT) != 0) drawLine( x * cell_width, y * cell_width, x * cell_width, (y + 1) * cell_width, g); if ((maze[x][y] & Constants.WALL_RIGHT) != 0) drawLine((x + 1) * cell_width, y * cell_width, (x + 1) * cell_width, (y + 1) * cell_width, g); } } } /* Draw a line, either in the SVG file or on the screen. */ public void drawLine(int x1, int y1, int x2, int y2, Graphics g) { if ( g != null ) g.drawLine(x1, y1, x2, y2); else System.out.format(" <line x1=\"%d\" y1=\"%d\"" + " x2=\"%d\" y2=\"%d\" />\n", x1, y1, x2, y2); } } Anyway, I was chugging along fairly quickly when I came to a bit that I just don't understand: /* Remember the surrounding squares, as we will */ for (var d = 0; d < 4; ++d) { if ((maze[][d][][d] & Constants.QUEUED) != 0) { /* want to connect them to the maze. */ todo[todonum++] = ((x + dx[d]) << Constants.QUEUED) | (y + dy[d]); maze[][d][][d] &= ~Constants.QUEUED; } } What I don't get is why there are four sets of brackets following the "maze" parameter instead of just two, since "maze" is a two dimensional array, not a four dimensional array. I'm sure there's a good reason for this. Problem is, I just don't get it. Thanks!

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  • Project Euler #15

    - by Aistina
    Hey everyone, Last night I was trying to solve challenge #15 from Project Euler: Starting in the top left corner of a 2×2 grid, there are 6 routes (without backtracking) to the bottom right corner. How many routes are there through a 20×20 grid? I figured this shouldn't be so hard, so I wrote a basic recursive function: const int gridSize = 20; // call with progress(0, 0) static int progress(int x, int y) { int i = 0; if (x < gridSize) i += progress(x + 1, y); if (y < gridSize) i += progress(x, y + 1); if (x == gridSize && y == gridSize) return 1; return i; } I verified that it worked for a smaller grids such as 2×2 or 3×3, and then set it to run for a 20×20 grid. Imagine my surprise when, 5 hours later, the program was still happily crunching the numbers, and only about 80% done (based on examining its current position/route in the grid). Clearly I'm going about this the wrong way. How would you solve this problem? I'm thinking it should be solved using an equation rather than a method like mine, but that's unfortunately not a strong side of mine. Update: I now have a working version. Basically it caches results obtained before when a n×m block still remains to be traversed. Here is the code along with some comments: // the size of our grid static int gridSize = 20; // the amount of paths available for a "NxM" block, e.g. "2x2" => 4 static Dictionary<string, long> pathsByBlock = new Dictionary<string, long>(); // calculate the surface of the block to the finish line static long calcsurface(long x, long y) { return (gridSize - x) * (gridSize - y); } // call using progress (0, 0) static long progress(long x, long y) { // first calculate the surface of the block remaining long surface = calcsurface(x, y); long i = 0; // zero surface means only 1 path remains // (we either go only right, or only down) if (surface == 0) return 1; // create a textual representation of the remaining // block, for use in the dictionary string block = (gridSize - x) + "x" + (gridSize - y); // if a same block has not been processed before if (!pathsByBlock.ContainsKey(block)) { // calculate it in the right direction if (x < gridSize) i += progress(x + 1, y); // and in the down direction if (y < gridSize) i += progress(x, y + 1); // and cache the result! pathsByBlock[block] = i; } // self-explanatory :) return pathsByBlock[block]; } Calling it 20 times, for grids with size 1×1 through 20×20 produces the following output: There are 2 paths in a 1 sized grid 0,0110006 seconds There are 6 paths in a 2 sized grid 0,0030002 seconds There are 20 paths in a 3 sized grid 0 seconds There are 70 paths in a 4 sized grid 0 seconds There are 252 paths in a 5 sized grid 0 seconds There are 924 paths in a 6 sized grid 0 seconds There are 3432 paths in a 7 sized grid 0 seconds There are 12870 paths in a 8 sized grid 0,001 seconds There are 48620 paths in a 9 sized grid 0,0010001 seconds There are 184756 paths in a 10 sized grid 0,001 seconds There are 705432 paths in a 11 sized grid 0 seconds There are 2704156 paths in a 12 sized grid 0 seconds There are 10400600 paths in a 13 sized grid 0,001 seconds There are 40116600 paths in a 14 sized grid 0 seconds There are 155117520 paths in a 15 sized grid 0 seconds There are 601080390 paths in a 16 sized grid 0,0010001 seconds There are 2333606220 paths in a 17 sized grid 0,001 seconds There are 9075135300 paths in a 18 sized grid 0,001 seconds There are 35345263800 paths in a 19 sized grid 0,001 seconds There are 137846528820 paths in a 20 sized grid 0,0010001 seconds 0,0390022 seconds in total I'm accepting danben's answer, because his helped me find this solution the most. But upvotes also to Tim Goodman and Agos :) Bonus update: After reading Eric Lippert's answer, I took another look and rewrote it somewhat. The basic idea is still the same but the caching part has been taken out and put in a separate function, like in Eric's example. The result is some much more elegant looking code. // the size of our grid const int gridSize = 20; // magic. static Func<A1, A2, R> Memoize<A1, A2, R>(this Func<A1, A2, R> f) { // Return a function which is f with caching. var dictionary = new Dictionary<string, R>(); return (A1 a1, A2 a2) => { R r; string key = a1 + "x" + a2; if (!dictionary.TryGetValue(key, out r)) { // not in cache yet r = f(a1, a2); dictionary.Add(key, r); } return r; }; } // calculate the surface of the block to the finish line static long calcsurface(long x, long y) { return (gridSize - x) * (gridSize - y); } // call using progress (0, 0) static Func<long, long, long> progress = ((Func<long, long, long>)((long x, long y) => { // first calculate the surface of the block remaining long surface = calcsurface(x, y); long i = 0; // zero surface means only 1 path remains // (we either go only right, or only down) if (surface == 0) return 1; // calculate it in the right direction if (x < gridSize) i += progress(x + 1, y); // and in the down direction if (y < gridSize) i += progress(x, y + 1); // self-explanatory :) return i; })).Memoize(); By the way, I couldn't think of a better way to use the two arguments as a key for the dictionary. I googled around a bit, and it seems this is a common solution. Oh well.

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  • How to display a JSON error message?

    - by Tiny Giant Studios
    I'm currently developing a tumblr theme and have built a jQuery JSON thingamabob that uses the Tumblr API to do the following: The user would click on the "post type" link (e.g. Video Posts), at which stage jQuery would use JSON to grab all the posts that's related to that type and then dynamically display them in a designated area. Now everything works absolutely peachy, except that with Tumblr being Tumblr and their servers taking a knock every now and then, the Tumblr API thingy is sometimes offline. Now I can't foresee when this function will be down, which is why I want to display some generic error message if JSON (for whatever reason) was unable to load the post. You'll see I've already written some code to show an error message when jQuery can't find any posts related to that post type BUT it doesn't cover any server errors. Note: I sometimes get this error: Failed to load resource: the server responded with a status of 503 (Service Temporarily Unavailable) It is for this 503 Error message that I need to write some code, but I'm slightly clueless :) Here's the jQuery JSON code: $('ul.right li').find('a').click(function() { var postType = this.className; var count = 0; byCategory(postType); return false; function byCategory(postType, callback) { $.getJSON('{URL}/api/read/json?type=' + postType + '&callback=?', function(data) { var article = []; $.each(data.posts, function(i, item) { // i = index // item = data for a particular post switch(item.type) { case 'photo': article[i] = '<div class="post_wrap"><div class="photo" style="padding-bottom:5px;">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/XSTldh6ds/photo_icon.png" alt="type_icon"/></a>' + '<a href="' + item.url + '" title="{Title}"><img src="' + item['photo-url-500'] + '"alt="image" /></a></div></div>'; count = 1; break; case 'video': article[i] = '<div class="post_wrap"><div class="video" style="padding-bottom:5px;">' + '<a href="' + item.url + '" title="{Title}" class="type_icon">' + '<img src="http://static.tumblr.com/ewjv7ap/nuSldhclv/video_icon.png" alt="type_icon"/></a>' + '<span style="margin: auto;">' + item['video-player'] + '</span>' + '</div></div>'; count = 1; break; case 'audio': if (use_IE == true) { article[i] = '<div class="post_wrap"><div class="regular">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/R50ldh5uj/audio_icon.png" alt="type_icon"/></a>' + '<h3><a href="' + item.url + '">' + item['id3-artist'] +' - ' + item['id3-title'] + '</a></h3>' + '</div></div>'; } else { article[i] = '<div class="post_wrap"><div class="regular">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/R50ldh5uj/audio_icon.png" alt="type_icon"/></a>' + '<h3><a href="' + item.url + '">' + item['id3-artist'] +' - ' + item['id3-title'] + '</a></h3><div class="player">' + item['audio-player'] + '</div>' + '</div></div>'; }; count = 1; break; case 'regular': article[i] = '<div class="post_wrap"><div class="regular">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/dwxldhck1/regular_icon.png" alt="type_icon"/></a><h3><a href="' + item.url + '">' + item['regular-title'] + '</a></h3><div class="description_container">' + item['regular-body'] + '</div></div></div>'; count = 1; break; case 'quote': article[i] = '<div class="post_wrap"><div class="quote">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/loEldhcpr/quote_icon.png" alt="type_icon"/></a><blockquote><h3><a href="' + item.url + '" title="{Title}">' + item['quote-text'] + '</a></h3></blockquote><cite>- ' + item['quote-source'] + '</cite></div></div>'; count = 1; break; case 'conversation': article[i] = '<div class="post_wrap"><div class="chat">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/MVuldhcth/conversation_icon.png" alt="type_icon"/></a><h3><a href="' + item.url + '">' + item['conversation-title'] + '</a></h3></div></div>'; count = 1; break; case 'link': article[i] = '<div class="post_wrap"><div class="link">' + '<a href="' + item.url + '" title="{Title}" class="type_icon"><img src="http://static.tumblr.com/ewjv7ap/EQGldhc30/link_icon.png" alt="type_icon"/></a><h3><a href="' + item['link-url'] + '" target="_blank">' + item['link-text'] + '</a></h3></div></div>'; count = 1; break; default: alert('No Entries Found.'); }; }) // end each if (!(count == 0)) { $('#content_right') .hide('fast') .html('<div class="first_div"><span class="left_corner"></span><span class="right_corner"></span><h2>Displaying ' + postType + ' Posts Only</h2></div>' + article.join('')) .slideDown('fast') } else { $('#content_right') .hide('fast') .html('<div class="first_div"><span class="left_corner"></span><span class="right_corner"></span><h2>Hmmm, currently there are no ' + postType + ' posts to display</h2></div>') .slideDown('fast') } // end getJSON }); // end byCategory } }); If you'd like to see the demo in action, check out Elegantem but do note that everything might work absolutely fine for you (or not), depending on Tumblr's temperament.

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  • Maze not generating properly. Out of bounds exception. need quick fix

    - by Dan Joseph Porcioncula
    My maze generator seems to have a problem. I am trying to generate something like the maze from http://mazeworks.com/mazegen/mazetut/index.htm . My program displays this http://a1.sphotos.ak.fbcdn.net/hphotos-ak-snc7/s320x320/374060_426350204045347_100000111130260_1880768_1572427285_n.jpg and the error Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at Grid.genRand(Grid.java:73) at Grid.main(Grid.java:35) How do I fix my generator program? import java.awt.*; import java.awt.Color; import java.awt.Component; import java.awt.Graphics; import javax.swing.*; import java.util.ArrayList; public class Grid extends Canvas { Cell[][] maze; int size; int pathSize; double width, height; ArrayList<int[]> coordinates = new ArrayList<int[]>(); public Grid(int size, int h, int w) { this.size = size; maze = new Cell[size][size]; for(int i = 0; i<size; i++){ for(int a =0; a<size; a++){ maze[i][a] = new Cell(); } } setPreferredSize(new Dimension(h, w)); } public static void main(String[] args) { JFrame y = new JFrame(); y.setLayout(new BorderLayout()); Grid f = new Grid(25, 400, 400); y.add(f, BorderLayout.CENTER); y.setSize(450, 450); y.setVisible(true); y.setDefaultCloseOperation(y.EXIT_ON_CLOSE); f.genRand(); f.repaint(); } public void push(int[] xy) { coordinates.add(xy); int i = coordinates.size(); coordinates.ensureCapacity(i++); } public int[] pop() { int[] x = coordinates.get((coordinates.size())-1); coordinates.remove((coordinates.size())-1); return x; } public int[] top() { return coordinates.get((coordinates.size())-1); } public void genRand(){ // create a CellStack (LIFO) to hold a list of cell locations [x] // set TotalCells = number of cells in grid int TotalCells = size*size; // choose a cell at random and call it CurrentCell int m = randomInt(size); int n = randomInt(size); Cell curCel = maze[m][n]; // set VisitedCells = 1 int visCel = 1,d=0; int[] q; int h,o = 0,p = 0; // while VisitedCells < TotalCells while( visCel < TotalCells){ // find all neighbors of CurrentCell with all walls intact if(maze[m-1][n].countWalls() == 4){d++;} if(maze[m+1][n].countWalls() == 4){d++;} if(maze[m][n-1].countWalls() == 4){d++;} if(maze[m][n+1].countWalls() == 4){d++;} // if one or more found if(d!=0){ Point[] ls = new Point[4]; ls[0] = new Point(m-1,n); ls[1] = new Point(m+1,n); ls[2] = new Point(m,n-1); ls[3] = new Point(m,n+1); // knock down the wall between it and CurrentCell h = randomInt(3); switch(h){ case 0: o = (int)(ls[0].getX()); p = (int)(ls[0].getY()); curCel.destroyWall(2); maze[o][p].destroyWall(1); break; case 1: o = (int)(ls[1].getX()); p = (int)(ls[1].getY()); curCel.destroyWall(1); maze[o][p].destroyWall(2); break; case 2: o = (int)(ls[2].getX()); p = (int)(ls[2].getY()); curCel.destroyWall(3); maze[o][p].destroyWall(0); break; case 3: o = (int)(ls[3].getX()); p = (int)(ls[3].getY()); curCel.destroyWall(0); maze[o][p].destroyWall(3); break; } // push CurrentCell location on the CellStack push(new int[] {m,n}); // make the new cell CurrentCell m = o; n = p; curCel = maze[m][n]; // add 1 to VisitedCells visCel++; } // else else{ // pop the most recent cell entry off the CellStack q = pop(); m = q[0]; n = q[1]; curCel = maze[m][n]; // make it CurrentCell // endIf } // endWhile } } public int randomInt(int s) { return (int)(s* Math.random());} public void paint(Graphics g) { int k, j; width = getSize().width; height = getSize().height; double htOfRow = height / (size); double wdOfRow = width / (size); //checks verticals - destroys east border of cell for (k = 0; k < size; k++) { for (j = 0; j < size; j++) { if(maze[k][j].checkWall(2)){ g.drawLine((int) (k * wdOfRow), (int) (j * htOfRow), (int) (k * wdOfRow), (int) ((j+1) * htOfRow)); }} } //checks horizontal - destroys north border of cell for (k = 0; k < size; k++) { for (j = 0; j < size; j++) { if(maze[k][j].checkWall(3)){ g.drawLine((int) (k * wdOfRow), (int) (j * htOfRow), (int) ((k+1) * wdOfRow), (int) (j * htOfRow)); }} } } } class Cell { private final static int NORTH = 0; private final static int EAST = 1; private final static int WEST = 2; private final static int SOUTH = 3; private final static int NO = 4; private final static int START = 1; private final static int END = 2; boolean[] wall = new boolean[4]; boolean[] border = new boolean[4]; boolean[] backtrack = new boolean[4]; boolean[] solution = new boolean[4]; private boolean isVisited = false; private int Key = 0; public Cell(){ for(int i=0;i<4;i++){wall[i] = true;} } public int countWalls(){ int i, k =0; for(i=0; i<4; i++) { if (wall[i] == true) {k++;} } return k;} public boolean checkWall(int x){ switch(x){ case 0: return wall[0]; case 1: return wall[1]; case 2: return wall[2]; case 3: return wall[3]; } return true; } public void destroyWall(int x){ switch(x){ case 0: wall[0] = false; break; case 1: wall[1] = false; break; case 2: wall[2] = false; break; case 3: wall[3] = false; break; } } public void setStart(int i){Key = i;} public int getKey(){return Key;} public boolean checkVisit(){return isVisited;} public void visitCell(){isVisited = true;} }

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  • cannot access a site from Mac OSX Lion but can from other machines on network?

    - by house9
    SOLVED: The issue is with the hamachi client, hamachi is hi-jacking all of the 5.0.0.0/8 address block http://en.wikipedia.org/wiki/Hamachi_(software)#Criticism http://b.logme.in/2012/11/07/changes-to-hamachi-on-november-19th/ The fix on Mac LogMeIn Hamachi Preferences Settings Advanced Peer Connections IP protocol mode IPv6 only (default is both) If you can only connect to some of your network over IPv4 this 'fix' will NOT work for you ----- A few weeks ago I started using a service - https://semaphoreapp.com I think they made DNS changes a week ago and ever since I cannot access the site from my Mac OSX Lion (10.7.4) machine (my main development machine) but I can access the site from other machines on my network ipad windows machine MacMini (10.6.8) After some google searching I tried both of these dscacheutil -flushcache sudo killall -HUP mDNSResponder but no go, I've contacted semaphoreapp as well, but nothing so far - also of interest, one of my colleagues has the exact same problem, cannot access via Mac OSX Lion but can via windows machine, we work remotely and are not on the same ISP some additional info Lion (10.7.4) cannot access site host semaphoreapp.com semaphoreapp.com has address 5.9.53.16 ping semaphoreapp.com PING semaphoreapp.com (5.9.53.16): 56 data bytes Request timeout for icmp_seq 0 Request timeout for icmp_seq 1 Request timeout for icmp_seq 2 Request timeout for icmp_seq 3 ping: sendto: No route to host Request timeout for icmp_seq 4 ping: sendto: Host is down Request timeout for icmp_seq 5 ping: sendto: Host is down Request timeout for icmp_seq 6 ping: sendto: Host is down Request timeout for icmp_seq 7 .... traceroute semaphoreapp.com traceroute to semaphoreapp.com (5.9.53.16), 64 hops max, 52 byte packets 1 * * * 2 * * * traceroute: sendto: No route to host 3 traceroute: wrote semaphoreapp.com 52 chars, ret=-1 *traceroute: sendto: Host is down traceroute: wrote semaphoreapp.com 52 chars, ret=-1 .... and MacMini (10.6.8) can access it host semaphoreapp.com semaphoreapp.com has address 5.9.53.16 ping semaphoreapp.com PING semaphoreapp.com (5.9.53.16): 56 data bytes 64 bytes from 5.9.53.16: icmp_seq=0 ttl=44 time=191.458 ms 64 bytes from 5.9.53.16: icmp_seq=1 ttl=44 time=202.923 ms 64 bytes from 5.9.53.16: icmp_seq=2 ttl=44 time=180.746 ms 64 bytes from 5.9.53.16: icmp_seq=3 ttl=44 time=200.616 ms 64 bytes from 5.9.53.16: icmp_seq=4 ttl=44 time=178.818 ms .... traceroute semaphoreapp.com traceroute to semaphoreapp.com (5.9.53.16), 64 hops max, 52 byte packets 1 192.168.0.1 (192.168.0.1) 1.677 ms 1.446 ms 1.445 ms 2 * LOCAL ISP 11.957 ms * 3 etc... 10.704 ms 14.183 ms 9.341 ms 4 etc... 32.641 ms 12.147 ms 10.850 ms 5 etc.... 44.205 ms 54.563 ms 36.243 ms 6 vlan139.car1.seattle1.level3.net (4.53.145.165) 50.136 ms 45.873 ms 30.396 ms 7 ae-32-52.ebr2.seattle1.level3.net (4.69.147.182) 31.926 ms 40.507 ms 49.993 ms 8 ae-2-2.ebr2.denver1.level3.net (4.69.132.54) 78.129 ms 59.674 ms 49.905 ms 9 ae-3-3.ebr1.chicago2.level3.net (4.69.132.62) 99.019 ms 82.008 ms 76.074 ms 10 ae-1-100.ebr2.chicago2.level3.net (4.69.132.114) 96.185 ms 75.658 ms 75.662 ms 11 ae-6-6.ebr2.washington12.level3.net (4.69.148.145) 104.322 ms 105.563 ms 118.480 ms 12 ae-5-5.ebr2.washington1.level3.net (4.69.143.221) 93.646 ms 99.423 ms 96.067 ms 13 ae-41-41.ebr2.paris1.level3.net (4.69.137.49) 177.744 ms ae-44-44.ebr2.paris1.level3.net (4.69.137.61) 199.363 ms 198.405 ms 14 ae-47-47.ebr1.frankfurt1.level3.net (4.69.143.141) 176.876 ms ae-45-45.ebr1.frankfurt1.level3.net (4.69.143.133) 170.994 ms ae-46-46.ebr1.frankfurt1.level3.net (4.69.143.137) 177.308 ms 15 ae-61-61.csw1.frankfurt1.level3.net (4.69.140.2) 176.769 ms ae-91-91.csw4.frankfurt1.level3.net (4.69.140.14) 178.676 ms 173.644 ms 16 ae-2-70.edge7.frankfurt1.level3.net (4.69.154.75) 180.407 ms ae-3-80.edge7.frankfurt1.level3.net (4.69.154.139) 174.861 ms 176.578 ms 17 as33891-net.edge7.frankfurt1.level3.net (195.16.162.94) 175.448 ms 185.658 ms 177.081 ms 18 hos-bb1.juniper4.rz16.hetzner.de (213.239.240.202) 188.700 ms 190.332 ms 188.196 ms 19 hos-tr4.ex3k14.rz16.hetzner.de (213.239.233.98) 199.632 ms hos-tr3.ex3k14.rz16.hetzner.de (213.239.233.66) 185.938 ms hos-tr2.ex3k14.rz16.hetzner.de (213.239.230.34) 182.378 ms 20 * * * 21 * * * 22 * * * any ideas? EDIT: adding tcpdump MacMini (which can connect) while running - ping semaphoreapp.com sudo tcpdump -v -i en0 dst semaphoreapp.com Password: tcpdump: listening on en0, link-type EN10MB (Ethernet), capture size 65535 bytes 17:33:03.337165 IP (tos 0x0, ttl 64, id 20153, offset 0, flags [none], proto ICMP (1), length 84, bad cksum 0 (->3129)!) 192.168.0.6 > static.16.53.9.5.clients.your-server.de: ICMP echo request, id 61918, seq 0, length 64 17:33:04.337279 IP (tos 0x0, ttl 64, id 26049, offset 0, flags [none], proto ICMP (1), length 84, bad cksum 0 (->1a21)!) 192.168.0.6 > static.16.53.9.5.clients.your-server.de: ICMP echo request, id 61918, seq 1, length 64 17:33:05.337425 IP (tos 0x0, ttl 64, id 47854, offset 0, flags [none], proto ICMP (1), length 84, bad cksum 0 (->c4f3)!) 192.168.0.6 > static.16.53.9.5.clients.your-server.de: ICMP echo request, id 61918, seq 2, length 64 17:33:06.337548 IP (tos 0x0, ttl 64, id 24772, offset 0, flags [none], proto ICMP (1), length 84, bad cksum 0 (->1f1e)!) 192.168.0.6 > static.16.53.9.5.clients.your-server.de: ICMP echo request, id 61918, seq 3, length 64 17:33:07.337670 IP (tos 0x0, ttl 64, id 8171, offset 0, flags [none], proto ICMP (1), length 84, bad cksum 0 (->5ff7)!) 192.168.0.6 > static.16.53.9.5.clients.your-server.de: ICMP echo request, id 61918, seq 4, length 64 17:33:08.337816 IP (tos 0x0, ttl 64, id 35810, offset 0, flags [none], proto ICMP (1), length 84, bad cksum 0 (->f3ff)!) 192.168.0.6 > static.16.53.9.5.clients.your-server.de: ICMP echo request, id 61918, seq 5, length 64 17:33:09.337948 IP (tos 0x0, ttl 64, id 31120, offset 0, flags [none], proto ICMP (1), length 84, bad cksum 0 (->652)!) 192.168.0.6 > static.16.53.9.5.clients.your-server.de: ICMP echo request, id 61918, seq 6, length 64 ^C 7 packets captured 1047 packets received by filter 0 packets dropped by kernel OSX Lion (cannot connect) while running - ping semaphoreapp.com # wireless ~ $ sudo tcpdump -v -i en1 dst semaphoreapp.com Password: tcpdump: listening on en1, link-type EN10MB (Ethernet), capture size 65535 bytes ^C 0 packets captured 262 packets received by filter 0 packets dropped by kernel and # wired ~ $ sudo tcpdump -v -i en0 dst semaphoreapp.com tcpdump: listening on en0, link-type EN10MB (Ethernet), capture size 65535 bytes ^C 0 packets captured 219 packets received by filter 0 packets dropped by kernel above output after Request timeout for icmp_seq 25 or 30 times from ping. I don't know much about tcpdump, but to me it doesn't seem like the ping requests are leaving my machine?

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  • Having trouble binding a ksoap object to an ArrayList in Android

    - by Maskau
    I'm working on an app that calls a web service, then the webservice returns an array list. My problem is I am having trouble getting the data into the ArrayList and then displaying in a ListView. Any ideas what I am doing wrong? I know for a fact the web service returns an ArrayList. Everything seems to be working fine, just no data in the ListView or the ArrayList.....Thanks in advance! EDIT: So I added more code to the catch block of run() and now it's returning "org.ksoap2.serialization.SoapObject".....no more no less....and I am even more confused now... package com.maskau; import java.util.ArrayList; import org.ksoap2.SoapEnvelope; import org.ksoap2.serialization.PropertyInfo; import org.ksoap2.serialization.SoapObject; import org.ksoap2.serialization.SoapSerializationEnvelope; import org.ksoap2.transport.AndroidHttpTransport; import android.app.*; import android.os.*; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.EditText; import android.widget.ListView; import android.widget.TextView; import android.view.View; import android.view.View.OnClickListener; public class Home extends Activity implements Runnable{ /** Called when the activity is first created. */ public static final String SOAP_ACTION = "http://bb.mcrcog.com/GetArtist"; public static final String METHOD_NAME = "GetArtist"; public static final String NAMESPACE = "http://bb.mcrcog.com"; public static final String URL = "http://bb.mcrcog.com/karaoke/service.asmx"; String wt; public static ProgressDialog pd; TextView text1; ListView lv; static EditText myEditText; static Button but; private ArrayList<String> Artist_Result = new ArrayList<String>(); @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main); myEditText = (EditText)findViewById(R.id.myEditText); text1 = (TextView)findViewById(R.id.text1); lv = (ListView)findViewById(R.id.lv); but = (Button)findViewById(R.id.but); but.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { wt = ("Searching for " + myEditText.getText().toString()); text1.setText(""); pd = ProgressDialog.show(Home.this, "Working...", wt , true, false); Thread thread = new Thread(Home.this); thread.start(); } } ); } public void run() { try { SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME); PropertyInfo pi = new PropertyInfo(); pi.setName("ArtistQuery"); pi.setValue(Home.myEditText.getText().toString()); request.addProperty(pi); SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11); envelope.dotNet = true; envelope.setOutputSoapObject(request); AndroidHttpTransport at = new AndroidHttpTransport(URL); at.call(SOAP_ACTION, envelope); java.util.Vector<Object> rs = (java.util.Vector<Object>)envelope.getResponse(); if (rs != null) { for (Object cs : rs) { Artist_Result.add(cs.toString()); } } } catch (Exception e) { // Added this line, throws "org.ksoap2.serialization.SoapObject" when run Artist_Result.add(e.getMessage()); } handler.sendEmptyMessage(0); } private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { ArrayAdapter<String> aa; aa = new ArrayAdapter<String>(Home.this, android.R.layout.simple_list_item_1, Artist_Result); lv.setAdapter(aa); try { if (Artist_Result.isEmpty()) { text1.setText("No Results"); } else { text1.setText("Complete"); myEditText.setText("Search Artist"); } } catch(Exception e) { text1.setText(e.getMessage()); } aa.notifyDataSetChanged(); pd.dismiss(); } }; }

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  • Searching for Windows User SID's in C#

    - by Ubiquitous Che
    Context Context first - issues I'm trying to resolve are below. One of our clients has asked as to quote how long it would take for us to improve one of our applications. This application currently provides basic user authentication in the form of username/password combinations. This client would like the ability for their employees to log-in using the details of whatever Windows User account is currently logged in at the time of running the application. It's not a deal-breaker if I tell them know - but the client might be willing to pay the costs of development to add this feature to the application. It's worth looking into. Based on my hunting around, it seems like storing the user login details against Domain\Username will be problematic if those details are changed. But Windows User SID's aren't supposed to change at all. I've got the impression that it would be best to record Windows Users by SID - feel free to relieve me of that if I'm wrong. I've been having a fiddle with some Windows API calls. From within C#, grabbing the current user's SID is easy enough. I can already take any user's SID and process it using LookupAccountSid to get username and domain for display purposes. For the interested, my code for this is at the end of this post. That's just the tip of the iceberg, however. The two issues below are completely outside my experience. Not only do I not know how to implement them - I don't even known how to find out how to implement them, or what the pitfalls are on various systems. Any help getting myself aimed in the right direction would be very much appreciated. Issue 1) Getting hold of the local user at runtime is meaningless if that user hasn't been granted access to the application. We will need to add a new section to our application's 'administrator console' for adding Windows Users (or groups) and assigning within-app permissions against those users. Something like an 'Add Windows User Login' button that will raise a pop-up window that will allow the user to search for available Windows User accounts on the network (not just the local machine) to be added to the list of available application logins. If there's already a component in .NET or Windows that I can shanghai into doing this for me, it would make me a very happy man. Issue 2) I also want to know how to take a given Windows User SID and check it against a given Windows User Group (probably taken from a database). I'm not sure how to get started with this one either, though I expect it to be easier than the issue above. For the Interested [STAThread] static void Main(string[] args) { MessageBox.Show(WindowsUserManager.GetAccountNameFromSID(WindowsIdentity.GetCurrent().User.Value)); MessageBox.Show(WindowsUserManager.GetAccountNameFromSID("S-1-5-21-57989841-842925246-1957994488-1003")); } public static class WindowsUserManager { public static string GetAccountNameFromSID(string SID) { try { StringBuilder name = new StringBuilder(); uint cchName = (uint)name.Capacity; StringBuilder referencedDomainName = new StringBuilder(); uint cchReferencedDomainName = (uint)referencedDomainName.Capacity; WindowsUserManager.SID_NAME_USE sidUse; int err = (int)ESystemError.ERROR_SUCCESS; if (!WindowsUserManager.LookupAccountSid(null, SID, name, ref cchName, referencedDomainName, ref cchReferencedDomainName, out sidUse)) { err = Marshal.GetLastWin32Error(); if (err == (int)ESystemError.ERROR_INSUFFICIENT_BUFFER) { name.EnsureCapacity((int)cchName); referencedDomainName.EnsureCapacity((int)cchReferencedDomainName); err = WindowsUserManager.LookupAccountSid(null, SID, name, ref cchName, referencedDomainName, ref cchReferencedDomainName, out sidUse) ? (int)ESystemError.ERROR_SUCCESS : Marshal.GetLastWin32Error(); } } if (err != (int)ESystemError.ERROR_SUCCESS) throw new ApplicationException(String.Format("Could not retrieve acount name from SID. {0}", SystemExceptionManager.GetDescription(err))); return String.Format(@"{0}\{1}", referencedDomainName.ToString(), name.ToString()); } catch (Exception ex) { if (ex is ApplicationException) throw ex; throw new ApplicationException("Could not retrieve acount name from SID", ex); } } private enum SID_NAME_USE { SidTypeUser = 1, SidTypeGroup, SidTypeDomain, SidTypeAlias, SidTypeWellKnownGroup, SidTypeDeletedAccount, SidTypeInvalid, SidTypeUnknown, SidTypeComputer } [DllImport("advapi32.dll", EntryPoint = "GetLengthSid", CharSet = CharSet.Auto)] private static extern int GetLengthSid(IntPtr pSID); [DllImport("advapi32.dll", SetLastError = true)] private static extern bool ConvertStringSidToSid( string StringSid, out IntPtr ptrSid); [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)] private static extern bool LookupAccountSid( string lpSystemName, [MarshalAs(UnmanagedType.LPArray)] byte[] Sid, StringBuilder lpName, ref uint cchName, StringBuilder ReferencedDomainName, ref uint cchReferencedDomainName, out SID_NAME_USE peUse); private static bool LookupAccountSid( string lpSystemName, string stringSid, StringBuilder lpName, ref uint cchName, StringBuilder ReferencedDomainName, ref uint cchReferencedDomainName, out SID_NAME_USE peUse) { byte[] SID = null; IntPtr SID_ptr = IntPtr.Zero; try { WindowsUserManager.ConvertStringSidToSid(stringSid, out SID_ptr); int err = SID_ptr == IntPtr.Zero ? Marshal.GetLastWin32Error() : (int)ESystemError.ERROR_SUCCESS; if (SID_ptr == IntPtr.Zero || err != (int)ESystemError.ERROR_SUCCESS) throw new ApplicationException(String.Format("'{0}' could not be converted to a SID byte array. {1}", stringSid, SystemExceptionManager.GetDescription(err))); int size = (int)GetLengthSid(SID_ptr); SID = new byte[size]; Marshal.Copy(SID_ptr, SID, 0, size); } catch (Exception ex) { if (ex is ApplicationException) throw ex; throw new ApplicationException(String.Format("'{0}' could not be converted to a SID byte array. {1}.", stringSid, ex.Message), ex); } finally { // Always want to release the SID_ptr (if it exists) to avoid memory leaks. if (SID_ptr != IntPtr.Zero) Marshal.FreeHGlobal(SID_ptr); } return WindowsUserManager.LookupAccountSid(lpSystemName, SID, lpName, ref cchName, ReferencedDomainName, ref cchReferencedDomainName, out peUse); } }

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  • std::basic_stringstream<unsigned char> won't compile with MSVC 10

    - by Michael J
    I'm trying to get UTF-8 chars to co-exist with ANSI 8-bit chars. My strategy has been to represent utf-8 chars as unsigned char so that appropriate overloads of functions can be used for the two character types. e.g. namespace MyStuff { typedef uchar utf8_t; typedef std::basic_string<utf8_t> U8string; } void SomeFunc(std::string &s); void SomeFunc(std::wstring &s); void SomeFunc(MyStuff::U8string &s); This all works pretty well until I try to use a stringstream. std::basic_ostringstream<MyStuff::utf8_t> ostr; ostr << 1; MSVC Visual C++ Express V10 won't compile this: c:\program files\microsoft visual studio 10.0\vc\include\xlocmon(213): warning C4273: 'id' : inconsistent dll linkage c:\program files\microsoft visual studio 10.0\vc\include\xlocnum(65) : see previous definition of 'public: static std::locale::id std::numpunct<unsigned char>::id' c:\program files\microsoft visual studio 10.0\vc\include\xlocnum(65) : while compiling class template static data member 'std::locale::id std::numpunct<_Elem>::id' with [ _Elem=Tk::utf8_t ] c:\program files\microsoft visual studio 10.0\vc\include\xlocnum(1149) : see reference to function template instantiation 'const _Facet &std::use_facet<std::numpunct<_Elem>>(const std::locale &)' being compiled with [ _Facet=std::numpunct<Tk::utf8_t>, _Elem=Tk::utf8_t ] c:\program files\microsoft visual studio 10.0\vc\include\xlocnum(1143) : while compiling class template member function 'std::ostreambuf_iterator<_Elem,_Traits> std::num_put<_Elem,_OutIt>:: do_put(_OutIt,std::ios_base &,_Elem,std::_Bool) const' with [ _Elem=Tk::utf8_t, _Traits=std::char_traits<Tk::utf8_t>, _OutIt=std::ostreambuf_iterator<Tk::utf8_t,std::char_traits<Tk::utf8_t>> ] c:\program files\microsoft visual studio 10.0\vc\include\ostream(295) : see reference to class template instantiation 'std::num_put<_Elem,_OutIt>' being compiled with [ _Elem=Tk::utf8_t, _OutIt=std::ostreambuf_iterator<Tk::utf8_t,std::char_traits<Tk::utf8_t>> ] c:\program files\microsoft visual studio 10.0\vc\include\ostream(281) : while compiling class template member function 'std::basic_ostream<_Elem,_Traits> & std::basic_ostream<_Elem,_Traits>::operator <<(int)' with [ _Elem=Tk::utf8_t, _Traits=std::char_traits<Tk::utf8_t> ] c:\program files\microsoft visual studio 10.0\vc\include\sstream(526) : see reference to class template instantiation 'std::basic_ostream<_Elem,_Traits>' being compiled with [ _Elem=Tk::utf8_t, _Traits=std::char_traits<Tk::utf8_t> ] c:\users\michael\dvl\tmp\console\console.cpp(23) : see reference to class template instantiation 'std::basic_ostringstream<_Elem,_Traits,_Alloc>' being compiled with [ _Elem=Tk::utf8_t, _Traits=std::char_traits<Tk::utf8_t>, _Alloc=std::allocator<uchar> ] . c:\program files\microsoft visual studio 10.0\vc\include\xlocmon(213): error C2491: 'std::numpunct<_Elem>::id' : definition of dllimport static data member not allowed with [ _Elem=Tk::utf8_t ] Any ideas? ** Edited 19 June 2012 ** OK, I've gotten closer to understanding this, but not how to solve it. As we all know, static class variables get defined twice: once in the class definition and once outside the class definition which establishes storage space. e.g. // in .h file class CFoo { // ... static int x; }; // in .cpp file int CFoo::x = 42; Now in the VC10 headers we get something like this: template<class _Elem> class numpunct : public locale::facet { // ... _CRTIMP2_PURE static locale::id id; // ... } When the header is included in an application, _CRTIMP2_PURE is defined as __declspec(dllimport), which means that the variable is imported from a dll. Now the header also contains the following template<class _Elem> locale::id numpunct<_Elem>::id; Note the absence of the __declspec(dllimport) qualifier. i.e. The class declaration says that the static linkage of the id variable is in the dll, but for the general case, it gets declared outside the dll. For the known cases, there are specialisations. template locale::id numpunct<char>::id; template locale::id numpunct<wchar_t>::id; These are protected by #ifs so that they are only included when building the DLL. They are excluded otherwise. i.e. the char and wchar_t versions of numpunct ARE inside the dll So we have the class definition saying that id's storage is in the DLL, but that is only true for the char and wchar_t specialisations, meaning that my unsigned char version is doomed. :-( The only way forward that I can think of is to create my own specialisation: basically copying it from the header file and fixing it. This raises many issues. Anybody have a better idea?

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  • click buttons error

    - by sara
    I will retrieve student information (id -number- name) from a database (MySQL) as a list view, each student have 2 buttons (delete - alert ) and radio buttons Every thing is ok, but how can I make an onClickListener, for example for the delete button because I try lots of examples, I heard that I can use (custom list or get view or direct onClickListener as in my code (but it is not working ) or Simple Cursor Adapter) I do not know what to use, I looked around for examples that can help me, but in my case but I did not find any so I hope this be reference for anyone have the same problem. this is my code which I use direct onClick with Simple Adapter public class ManageSection extends ListActivity { //ProgresogressDialog pDialog; private ProgressDialog pDialog; // Creating JSON Parser object // Creating JSON Parser object JSONParser jParser = new JSONParser(); //class boolean x =true; Button delete; ArrayList<HashMap<String, String>> studentList; //url to get all products list private static String url_all_student = "http://10.0.2.2/SmsPhp/view_student_info.php"; String cl; // JSON Node names private static final String TAG_SUCCESS = "success"; private static final String TAG_student = "student"; private static final String TAG_StudentID = "StudentID"; private static final String TAG_StudentNo = "StudentNo"; private static final String TAG_FullName = "FullName"; private static final String TAG_Avatar="Avatar"; HashMap<String, String> selected_student; // course JSONArray JSONArray student = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.manage_section); studentList = new ArrayList<HashMap<String, String>>(); ListView list1 = getListView(); list1.setAdapter(getListAdapter()); list1.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> adapterView, View view, int pos, long l) { selected_student =(HashMap<String, String>) studentList.get(pos); //member of your activity. delete =(Button)view.findViewById(R.id.DeleteStudent); cl=selected_student.get(TAG_StudentID); Toast.makeText(getBaseContext(),cl,Toast.LENGTH_LONG).show(); delete.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { Log.d("id: ",cl); Toast.makeText(getBaseContext(),cl,Toast.LENGTH_LONG).show(); } }); } }); new LoadAllstudent().execute(); } /** * Background Async Task to Load all student by making HTTP Request * */ class LoadAllstudent extends AsyncTask<String, String, String> { /** * Before starting background thread Show Progress Dialog * */ @Override protected void onPreExecute() { super.onPreExecute(); pDialog = new ProgressDialog(ManageSection.this); pDialog.setMessage("Loading student. Please wait..."); pDialog.setIndeterminate(false); } /** * getting All student from u r l * */ @Override protected String doInBackground(String... args) { // Building Parameters List<NameValuePair> params = new ArrayList<NameValuePair>(); // getting JSON string from URL JSONObject json = jParser.makeHttpRequest(url_all_student, "GET", params); // Check your log cat for JSON response Log.d("All student : ", json.toString()); try { // Checking for SUCCESS TAG int success = json.getInt(TAG_SUCCESS); if (success == 1) { // student found // Getting Array of course student = json.getJSONArray(TAG_student); // looping through All courses for (int i = 0; i < student.length(); i++)//course JSONArray { JSONObject c = student.getJSONObject(i); // read first // Storing each json item in variable String StudentID = c.getString(TAG_StudentID); String StudentNo = c.getString(TAG_StudentNo); String FullName = c.getString(TAG_FullName); // String Avatar = c.getString(TAG_Avatar); // creating new HashMap HashMap<String, String> map = new HashMap<String, String>(); // adding each child node to HashMap key => value map.put(TAG_StudentID, StudentID); map.put(TAG_StudentNo, StudentNo); map.put(TAG_FullName, FullName); // adding HashList to ArrayList studentList.add(map); } } else { x=false; } } catch (JSONException e) { e.printStackTrace(); } return null; } /** * After completing background task Dismiss the progress dialog * **/ protected void onPostExecute(String file_url) { // dismiss the dialog after getting all products pDialog.dismiss(); if (x==false) Toast.makeText(getBaseContext(),"no student" ,Toast.LENGTH_LONG).show(); ListAdapter adapter = new SimpleAdapter( ManageSection.this, studentList, R.layout.list_student, new String[] { TAG_StudentID, TAG_StudentNo,TAG_FullName}, new int[] { R.id.StudentID, R.id.StudentNo,R.id.FullName}); setListAdapter(adapter); // Updating parsed JSON data into ListView } } } So what do you think, why doesn't the delete button work? There is no error in my log cat. What is the alternative way ?.. what should I do ?

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  • Java Array Index Out of Bounds Exception

    - by user1302023
    I need help debugging the following program: I'm getting a run time error that reads: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at SearchEngine.main(SearchEngine.java:126) import java.util.*; import java.io.*; public class SearchEngine { public static int getNumberOfWords (File f) throws FileNotFoundException { int numWords = 0; Scanner scan = new Scanner(f); while (scan.hasNext()) { numWords++; scan.next(); } scan.close(); return numWords; } public static void readInWords (File input, String [] x) throws FileNotFoundException { Scanner scan = new Scanner(input); int i = 0; while (scan.hasNext() && i<x.length) { x[i] = scan.next(); i++; } scan.close(); } public static int getNumOfDistinctWords (File input, String [] x) throws FileNotFoundException { Scanner scan = new Scanner(input); int count = 0; int i = 1; while (scan.hasNext() && i<x.length) { if (!x[i].equals(x[i-1])) { count++; } i++; } scan.close(); return count; } public static void readInDistinctWords (String [] x, String [] y) { int i = 1; int k = 0; while (i<x.length) { if (!x[i].equals(x[i-1])) { y[k] = x[i]; k++; } i++; } } public static int getNumberOfLines (File input) throws FileNotFoundException { int numLines = 0; Scanner scan = new Scanner(input); while (scan.hasNextLine()) { numLines++; scan.nextLine(); } scan.close(); return numLines; } public static void readInLines (File input, String [] x) throws FileNotFoundException { Scanner scan = new Scanner(input); int i = 0; while (scan.hasNextLine() && i<x.length) { x[i] = scan.nextLine(); i++; } scan.close(); } public static void main(String [] args) { try { //gets file name System.out.println("Enter the name of the text file you wish to search"); Scanner kb = new Scanner(System.in); String fileName = kb.nextLine(); String TXT = ".txt"; if (!fileName.endsWith(TXT)) { fileName = fileName.concat(TXT); } File input = new File(fileName); //First part of creating index System.out.println("Creating vocabArray"); int NUM_WORDS = getNumberOfWords(input); //System.out.println(NUM_WORDS); String [] wordArray = new String[NUM_WORDS]; readInWords(input, wordArray); Arrays.sort(wordArray); int NUM_DISTINCT_WORDS = getNumOfDistinctWords(input, wordArray); String [] vocabArray = new String[NUM_DISTINCT_WORDS]; readInDistinctWords(wordArray, vocabArray); System.out.println("Finished creating vocabArray"); System.out.println("Creating concordanceArray"); int NUM_LINES = getNumberOfLines(input); String [] concordanceArray = new String[NUM_LINES]; readInLines(input, concordanceArray); System.out.println("Finished creating concordanceArray"); System.out.println("Creating invertedIndex"); int [][] invertedIndex = new int[NUM_DISTINCT_WORDS][10]; int [] wordCountArray = new int[NUM_DISTINCT_WORDS]; int lineNum = 0; while (lineNum<concordanceArray.length) { Scanner scan = new Scanner(concordanceArray[lineNum]); while (scan.hasNext()) { int wordPos = Arrays.binarySearch(vocabArray, scan.next()); wordCountArray[wordPos]+=1; for(int i = 0; i < invertedIndex.length; i++) { for(int j = 0; j < invertedIndex[i].length; j++) { if (invertedIndex[i][j] == 0) { invertedIndex[i][j] = lineNum; break; } } } } lineNum++; } System.out.println("Finished creating invertedIndex"); } catch (FileNotFoundException exception) { System.out.println("File Not Found"); } } //main } //class

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  • How to give position zero of spinner a prompt value?

    - by Eugene H
    The database is then transferring the data to a spinner which I want to leave position 0 blank so I can add a item to the spinner with no value making it look like a prompt. I have been going at it all day. FAil after Fail MainActivity public class MainActivity extends Activity { Button AddBtn; EditText et; EditText cal; Spinner spn; SQLController SQLcon; ProgressDialog PD; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); AddBtn = (Button) findViewById(R.id.addbtn_id); et = (EditText) findViewById(R.id.et_id); cal = (EditText) findViewById(R.id.et_cal); spn = (Spinner) findViewById(R.id.spinner_id); spn.setOnItemSelectedListener(new OnItemSelectedListenerWrapper( new OnItemSelectedListener() { @Override public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) { SQLcon.open(); Cursor c = SQLcon.readData(); if (c.moveToPosition(pos)) { String name = c.getString(c .getColumnIndex(DBhelper.MEMBER_NAME)); String calories = c.getString(c .getColumnIndex(DBhelper.KEY_CALORIES)); et.setText(name); cal.setText(calories); } SQLcon.close(); // closing database } @Override public void onNothingSelected(AdapterView<?> parent) { // TODO Auto-generated method stub } })); SQLcon = new SQLController(this); // opening database SQLcon.open(); loadtospinner(); AddBtn.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { new MyAsync().execute(); } }); } public void loadtospinner() { ArrayList<String> al = new ArrayList<String>(); Cursor c = SQLcon.readData(); c.moveToFirst(); while (!c.isAfterLast()) { String name = c.getString(c.getColumnIndex(DBhelper.MEMBER_NAME)); String calories = c.getString(c .getColumnIndex(DBhelper.KEY_CALORIES)); al.add(name + ", Calories: " + calories); c.moveToNext(); } ArrayAdapter<String> aa1 = new ArrayAdapter<String>( getApplicationContext(), android.R.layout.simple_spinner_item, al); spn.setAdapter(aa1); // closing database SQLcon.close(); } private class MyAsync extends AsyncTask<Void, Void, Void> { @Override protected void onPreExecute() { super.onPreExecute(); PD = new ProgressDialog(MainActivity.this); PD.setTitle("Please Wait.."); PD.setMessage("Loading..."); PD.setCancelable(false); PD.show(); } @Override protected Void doInBackground(Void... params) { String name = et.getText().toString(); String calories = cal.getText().toString(); // opening database SQLcon.open(); // insert data into table SQLcon.insertData(name, calories); return null; } @Override protected void onPostExecute(Void result) { super.onPostExecute(result); loadtospinner(); PD.dismiss(); } } } DataBase public class SQLController { private DBhelper dbhelper; private Context ourcontext; private SQLiteDatabase database; public SQLController(Context c) { ourcontext = c; } public SQLController open() throws SQLException { dbhelper = new DBhelper(ourcontext); database = dbhelper.getWritableDatabase(); return this; } public void close() { dbhelper.close(); } public void insertData(String name, String calories) { ContentValues cv = new ContentValues(); cv.put(DBhelper.MEMBER_NAME, name); cv.put(DBhelper.KEY_CALORIES, calories); database.insert(DBhelper.TABLE_MEMBER, null, cv); } public Cursor readData() { String[] allColumns = new String[] { DBhelper.MEMBER_ID, DBhelper.MEMBER_NAME, DBhelper.KEY_CALORIES }; Cursor c = database.query(DBhelper.TABLE_MEMBER, allColumns, null, null, null, null, null); if (c != null) { c.moveToFirst(); } return c; } } Helper public class DBhelper extends SQLiteOpenHelper { // TABLE INFORMATTION public static final String TABLE_MEMBER = "member"; public static final String MEMBER_ID = "_id"; public static final String MEMBER_NAME = "name"; public static final String KEY_CALORIES = "calories"; // DATABASE INFORMATION static final String DB_NAME = "MEMBER.DB"; static final int DB_VERSION = 2; // TABLE CREATION STATEMENT private static final String CREATE_TABLE = "create table " + TABLE_MEMBER + "(" + MEMBER_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + MEMBER_NAME + " TEXT NOT NULL," + KEY_CALORIES + " INT NOT NULL);"; public DBhelper(Context context) { super(context, DB_NAME, null, DB_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(CREATE_TABLE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub db.execSQL("DROP TABLE IF EXISTS " + TABLE_MEMBER); onCreate(db); } }

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  • These are few objective type questions which i was not able to find the solution [closed]

    - by Tarun
    1. Which of the following advantages does System.Collections.IDictionaryEnumerator provide over System.Collections.IEnumerator? a. It adds properties for direct access to both the Key and the Value b. It is optimized to handle the structure of a Dictionary. c. It provides properties to determine if the Dictionary is enumerated in Key or Value order d. It provides reverse lookup methods to distinguish a Key from a specific Value 2. When Implementing System.EnterpriseServices.ServicedComponent derived classes, which of the following statements are true? a. Enabling object pooling requires an attribute on the class and the enabling of pooling in the COM+ catalog. b. Methods can be configured to automatically mark a transaction as complete by the use of attributes. c. You can configure authentication using the AuthenticationOption when the ActivationMode is set to Library. d. You can control the lifecycle policy of an individual instance using the SetLifetimeService method. 3. Which of the following are true regarding event declaration in the code below? class Sample { event MyEventHandlerType MyEvent; } a. MyEventHandlerType must be derived from System.EventHandler or System.EventHandler<TEventArgs> b. MyEventHandlerType must take two parameters, the first of the type Object, and the second of a class derived from System.EventArgs c. MyEventHandlerType may have a non-void return type d. If MyEventHandlerType is a generic type, event declaration must use a specialization of that type. e. MyEventHandlerType cannot be declared static 4. Which of the following statements apply to developing .NET code, using .NET utilities that are available with the SDK or Visual Studio? a. Developers can create assemblies directly from the MSIL Source Code. b. Developers can examine PE header information in an assembly. c. Developers can generate XML Schemas from class definitions contained within an assembly. d. Developers can strip all meta-data from managed assemblies. e. Developers can split an assembly into multiple assemblies. 5. Which of the following characteristics do classes in the System.Drawing namespace such as Brush,Font,Pen, and Icon share? a. They encapsulate native resource and must be properly Disposed to prevent potential exhausting of resources. b. They are all MarshalByRef derived classes, but functionality across AppDomains has specific limitations. c. You can inherit from these classes to provide enhanced or customized functionality 6. Which of the following are required to be true by objects which are going to be used as keys in a System.Collections.HashTable? a. They must handle case-sensitivity identically in both the GetHashCode() and Equals() methods. b. Key objects must be immutable for the duration they are used within a HashTable. c. Get HashCode() must be overridden to provide the same result, given the same parameters, regardless of reference equalityl unless the HashTable constructor is provided with an IEqualityComparer parameter. d. Each Element in a HashTable is stored as a Key/Value pair of the type System.Collections.DictionaryElement e. All of the above 7. Which of the following are true about Nullable types? a. A Nullable type is a reference type. b. A Nullable type is a structure. c. An implicit conversion exists from any non-nullable value type to a nullable form of that type. d. An implicit conversion exists from any nullable value type to a non-nullable form of that type. e. A predefined conversion from the nullable type S? to the nullable type T? exists if there is a predefined conversion from the non-nullable type S to the non-nullable type T 8. When using an automatic property, which of the following statements is true? a. The compiler generates a backing field that is completely inaccessible from the application code. b. The compiler generates a backing field that is a private instance member with a leading underscore that can be programmatically referenced. c. The compiler generates a backing field that is accessible via reflection d. The compiler generates a code that will store the information separately from the instance to ensure its security. 9. Which of the following does using Initializer Syntax with a collection as shown below require? CollectionClass numbers = new CollectionClass { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; a. The Collection Class must implement System.Collections.Generic.ICollection<T> b. The Collection Class must implement System.Collections.Generic.IList<T> c. Each of the Items in the Initializer List will be passed to the Add<T>(T item) method d. The items in the initializer will be treated as an IEnumerable<T> and passed to the collection constructor+K110 10. What impact will using implicitly typed local variables as in the following example have? var sample = "Hello World"; a. The actual type is determined at compilation time, and has no impact on the runtime b. The actual type is determined at runtime, and late binding takes effect c. The actual type is based on the native VARIANT concept, and no binding to a specific type takes place. d. "var" itself is a specific type defined by the framework, and no special binding takes place 11. Which of the following is not supported by remoting object types? a. well-known singleton b. well-known single call c. client activated d. context-agile 12. In which of the following ways do structs differ from classes? a. Structs can not implement interfaces b. Structs cannot inherit from a base struct c. Structs cannot have events interfaces d. Structs cannot have virtual methods 13. Which of the following is not an unboxing conversion? a. void Sample1(object o) { int i = (int)o; } b. void Sample1(ValueType vt) { int i = (int)vt; } c. enum E { Hello, World} void Sample1(System.Enum et) { E e = (E) et; } d. interface I { int Value { get; set; } } void Sample1(I vt) { int i = vt.Value; } e. class C { public int Value { get; set; } } void Sample1(C vt) { int i = vt.Value; } 14. Which of the following are characteristics of the System.Threading.Timer class? a. The method provided by the TimerCallback delegate will always be invoked on the thread which created the timer. b. The thread which creates the timer must have a message processing loop (i.e. be considered a UI thread) c. The class contains protection to prevent reentrancy to the method provided by the TimerCallback delegate d. You can receive notification of an instance being Disposed by calling an overload of the Dispose method. 15. What is the proper declaration of a method which will handle the following event? Class MyClass { public event EventHandler MyEvent; } a. public void A_MyEvent(object sender, MyArgs e) { } b. public void A_MyEvent(object sender, EventArgs e) { } c. public void A_MyEvent(MyArgs e) { } d. public void A_MyEvent(MyClass sender,EventArgs e) { } 16. Which of the following scenarios are applicable to Window Workflow Foundation? a. Document-centric workflows b. Human workflows c. User-interface page flows d. Builtin support for communications across multiple applications and/or platforms e. All of the above 17. When using an automatic property, which of the following statements is true? a. The compiler generates a backing field that is completely inaccessible from the application code. b. The compiler generates a backing field that is a private instance member with a leading underscore that can be programmatically referenced. c. The compiler generates a backing field that is accessible via reflection d. The compiler generates a code that will store the information separately from the instance to ensure its security. 18 While using the capabilities supplied by the System.Messaging classes, which of the following are true? a. Information must be explicitly converted to/from a byte stream before it uses the MessageQueue class b. Invoking the MessageQueue.Send member defaults to using the System.Messaging.XmlMessageFormatter to serialize the object. c. Objects must be XMLSerializable in order to be transferred over a MessageQueue instance. d. The first entry in a MessageQueue must be removed from the queue before the next entry can be accessed e. Entries removed from a MessageQueue within the scope of a transaction, will be pushed back into the front of the queue if the transaction fails. 19. Which of the following are true about declarative attributes? a. They must be inherited from the System.Attribute. b. Attributes are instantiated at the same time as instances of the class to which they are applied. c. Attribute classes may be restricted to be applied only to application element types. d. By default, a given attribute may be applied multiple times to the same application element. 20. When using version 3.5 of the framework in applications which emit a dynamic code, which of the following are true? a. A Partial trust code can not emit and execute a code b. A Partial trust application must have the SecurityCriticalAttribute attribute have called Assert ReflectionEmit permission c. The generated code no more permissions than the assembly which emitted it. d. It can be executed by calling System.Reflection.Emit.DynamicMethod( string name, Type returnType, Type[] parameterTypes ) without any special permissions Within Windows Workflow Foundation, Compensating Actions are used for: a. provide a means to rollback a failed transaction b. provide a means to undo a successfully committed transaction later c. provide a means to terminate an in process transaction d. achieve load balancing by adapting to the current activity 21. What is the proper declaration of a method which will handle the following event? Class MyClass { public event EventHandler MyEvent; } a. public void A_MyEvent(object sender, MyArgs e) { } b. public void A_MyEvent(object sender, EventArgs e) { } c. public void A_MyEvent(MyArgs e) { } d. public void A_MyEvent(MyClass sender,EventArgs e) { } 22. Which of the following controls allows the use of XSL to transform XML content into formatted content? a. System.Web.UI.WebControls.Xml b. System.Web.UI.WebControls.Xslt c. System.Web.UI.WebControls.Substitution d. System.Web.UI.WebControls.Transform 23. To which of the following do automatic properties refer? a. You declare (explicitly or implicitly) the accessibility of the property and get and set accessors, but do not provide any implementation or backing field b. You attribute a member field so that the compiler will generate get and set accessors c. The compiler creates properties for your class based on class level attributes d. They are properties which are automatically invoked as part of the object construction process 24. Which of the following are true about Nullable types? a. A Nullable type is a reference type. b. An implicit conversion exists from any non-nullable value type to a nullable form of that type. c. A predefined conversion from the nullable type S? to the nullable type T? exists if there is a predefined conversion from the non-nullable type S to the non-nullable type T 25. When using an automatic property, which of the following statements is true? a. The compiler generates a backing field that is completely inaccessible from the application code. b. The compiler generates a backing field that is accessible via reflection. c. The compiler generates a code that will store the information separately from the instance to ensure its security. 26. When using an implicitly typed array, which of the following is most appropriate? a. All elements in the initializer list must be of the same type. b. All elements in the initializer list must be implicitly convertible to a known type which is the actual type of at least one member in the initializer list c. All elements in the initializer list must be implicitly convertible to common type which is a base type of the items actually in the list 27. Which of the following is false about anonymous types? a. They can be derived from any reference type. b. Two anonymous types with the same named parameters in the same order declared in different classes have the same type. c. All properties of an anonymous type are read/write. 28. Which of the following are true about Extension methods. a. They can be declared either static or instance members b. They must be declared in the same assembly (but may be in different source files) c. Extension methods can be used to override existing instance methods d. Extension methods with the same signature for the same class may be declared in multiple namespaces without causing compilation errors

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  • Parallelism in .NET – Part 7, Some Differences between PLINQ and LINQ to Objects

    - by Reed
    In my previous post on Declarative Data Parallelism, I mentioned that PLINQ extends LINQ to Objects to support parallel operations.  Although nearly all of the same operations are supported, there are some differences between PLINQ and LINQ to Objects.  By introducing Parallelism to our declarative model, we add some extra complexity.  This, in turn, adds some extra requirements that must be addressed. In order to illustrate the main differences, and why they exist, let’s begin by discussing some differences in how the two technologies operate, and look at the underlying types involved in LINQ to Objects and PLINQ . LINQ to Objects is mainly built upon a single class: Enumerable.  The Enumerable class is a static class that defines a large set of extension methods, nearly all of which work upon an IEnumerable<T>.  Many of these methods return a new IEnumerable<T>, allowing the methods to be chained together into a fluent style interface.  This is what allows us to write statements that chain together, and lead to the nice declarative programming model of LINQ: double min = collection .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Other LINQ variants work in a similar fashion.  For example, most data-oriented LINQ providers are built upon an implementation of IQueryable<T>, which allows the database provider to turn a LINQ statement into an underlying SQL query, to be performed directly on the remote database. PLINQ is similar, but instead of being built upon the Enumerable class, most of PLINQ is built upon a new static class: ParallelEnumerable.  When using PLINQ, you typically begin with any collection which implements IEnumerable<T>, and convert it to a new type using an extension method defined on ParallelEnumerable: AsParallel().  This method takes any IEnumerable<T>, and converts it into a ParallelQuery<T>, the core class for PLINQ.  There is a similar ParallelQuery class for working with non-generic IEnumerable implementations. This brings us to our first subtle, but important difference between PLINQ and LINQ – PLINQ always works upon specific types, which must be explicitly created. Typically, the type you’ll use with PLINQ is ParallelQuery<T>, but it can sometimes be a ParallelQuery or an OrderedParallelQuery<T>.  Instead of dealing with an interface, implemented by an unknown class, we’re dealing with a specific class type.  This works seamlessly from a usage standpoint – ParallelQuery<T> implements IEnumerable<T>, so you can always “switch back” to an IEnumerable<T>.  The difference only arises at the beginning of our parallelization.  When we’re using LINQ, and we want to process a normal collection via PLINQ, we need to explicitly convert the collection into a ParallelQuery<T> by calling AsParallel().  There is an important consideration here – AsParallel() does not need to be called on your specific collection, but rather any IEnumerable<T>.  This allows you to place it anywhere in the chain of methods involved in a LINQ statement, not just at the beginning.  This can be useful if you have an operation which will not parallelize well or is not thread safe.  For example, the following is perfectly valid, and similar to our previous examples: double min = collection .AsParallel() .Select(item => item.SomeOperation()) .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); However, if SomeOperation() is not thread safe, we could just as easily do: double min = collection .Select(item => item.SomeOperation()) .AsParallel() .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); In this case, we’re using standard LINQ to Objects for the Select(…) method, then converting the results of that map routine to a ParallelQuery<T>, and processing our filter (the Where method) and our aggregation (the Min method) in parallel. PLINQ also provides us with a way to convert a ParallelQuery<T> back into a standard IEnumerable<T>, forcing sequential processing via standard LINQ to Objects.  If SomeOperation() was thread-safe, but PerformComputation() was not thread-safe, we would need to handle this by using the AsEnumerable() method: double min = collection .AsParallel() .Select(item => item.SomeOperation()) .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .AsEnumerable() .Min(item => item.PerformComputation()); Here, we’re converting our collection into a ParallelQuery<T>, doing our map operation (the Select(…) method) and our filtering in parallel, then converting the collection back into a standard IEnumerable<T>, which causes our aggregation via Min() to be performed sequentially. This could also be written as two statements, as well, which would allow us to use the language integrated syntax for the first portion: var tempCollection = from item in collection.AsParallel() let e = item.SomeOperation() where (e.SomeProperty > 6 && e.SomeProperty < 24) select e; double min = tempCollection.AsEnumerable().Min(item => item.PerformComputation()); This allows us to use the standard LINQ style language integrated query syntax, but control whether it’s performed in parallel or serial by adding AsParallel() and AsEnumerable() appropriately. The second important difference between PLINQ and LINQ deals with order preservation.  PLINQ, by default, does not preserve the order of of source collection. This is by design.  In order to process a collection in parallel, the system needs to naturally deal with multiple elements at the same time.  Maintaining the original ordering of the sequence adds overhead, which is, in many cases, unnecessary.  Therefore, by default, the system is allowed to completely change the order of your sequence during processing.  If you are doing a standard query operation, this is usually not an issue.  However, there are times when keeping a specific ordering in place is important.  If this is required, you can explicitly request the ordering be preserved throughout all operations done on a ParallelQuery<T> by using the AsOrdered() extension method.  This will cause our sequence ordering to be preserved. For example, suppose we wanted to take a collection, perform an expensive operation which converts it to a new type, and display the first 100 elements.  In LINQ to Objects, our code might look something like: // Using IEnumerable<SourceClass> collection IEnumerable<ResultClass> results = collection .Select(e => e.CreateResult()) .Take(100); If we just converted this to a parallel query naively, like so: IEnumerable<ResultClass> results = collection .AsParallel() .Select(e => e.CreateResult()) .Take(100); We could very easily get a very different, and non-reproducable, set of results, since the ordering of elements in the input collection is not preserved.  To get the same results as our original query, we need to use: IEnumerable<ResultClass> results = collection .AsParallel() .AsOrdered() .Select(e => e.CreateResult()) .Take(100); This requests that PLINQ process our sequence in a way that verifies that our resulting collection is ordered as if it were processed serially.  This will cause our query to run slower, since there is overhead involved in maintaining the ordering.  However, in this case, it is required, since the ordering is required for correctness. PLINQ is incredibly useful.  It allows us to easily take nearly any LINQ to Objects query and run it in parallel, using the same methods and syntax we’ve used previously.  There are some important differences in operation that must be considered, however – it is not a free pass to parallelize everything.  When using PLINQ in order to parallelize your routines declaratively, the same guideline I mentioned before still applies: Parallelization is something that should be handled with care and forethought, added by design, and not just introduced casually.

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  • Entity Framework 4.0: Creating objects of correct type when using lazy loading

    - by DigiMortal
    In my posting about Entity Framework 4.0 and POCOs I introduced lazy loading in EF applications. EF uses proxy classes for lazy loading and this means we have new types in that come and go dynamically in runtime. We don’t have these types available when we write code but we cannot forget that EF may expect us to use dynamically generated types. In this posting I will give you simple hint how to use correct types in your code. The background of lazy loading and proxy classes As a first thing I will explain you in short what is proxy class. Business classes when designed correctly have no knowledge about their birth and death – they don’t know how they are created and they don’t know how their data is persisted. This is the responsibility of object runtime. When we use lazy loading we need a little bit different classes that know how to load data for properties when code accesses the property first time. As we cannot add this functionality to our business classes (they may be stored through more than one data access technology or by more than one Data Access Layer (DAL)) we create proxy classes that extend our business classes. If we have class called Product and product has lazy loaded property called Customer then we need proxy class, let’s say ProductProxy, that has same public signature as Product so we can use it INSTEAD OF product in our code. ProductProxy overrides Customer property. If customer is not asked then customer is null. But if we ask for Customer property then overridden property of ProductProxy loads it from database. This is how lazy loading works. Problem – two types for same thing As lazy loading may introduce dynamically generated proxy types we don’t know in our application code which type is returned. We cannot be sure that we have Product not ProductProxy returned. This leads us to the following question: how can we create Product of correct type if we don’t know the correct type? In EF solution is simple. Solution – use factory methods If you are using repositories and you are not using factories (imho it is pretty pointless with mapper) you can add factory methods to your EF based repositories. Take a look at this class. public class Event {     public int ID { get; set; }     public string Title { get; set; }     public string Location { get; set; }     public virtual Party Organizer { get; set; }     public DateTime Date { get; set; } } We have virtual member called Organizer. This property is virtual because we want to use lazy loading on this class so Organizer is loaded only when we ask it. EF provides us with method called CreateObject<T>(). CreateObject<T>() is member of ObjectContext class and it creates the object based on given type. In runtime proxy type for Event is created for us automatically and when we call CreateObject<T>() for Event it returns as object of Event proxy type. The factory method for events repository is as follows. public Event CreateEvent() {     var evt = _context.CreateObject<Event>();     return evt; } And we are done. Instead of creating factory classes we created factory methods that guarantee that created objects are of correct type. Conclusion Although lazy loading introduces some new objects we cannot use at design time because they live only in runtime we can write code without worrying about exact implementation type of object. This holds true until we have clean code and we don’t make any decisions based on object type. EF4.0 provides us with very simple factory method that create and return objects of correct type. All we had to do was adding factory methods to our repositories.

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  • Is code maintenance typically a special project, or is it considered part of daily work?

    - by blueberryfields
    Earlier, I asked to find out which tools are commonly used to monitor methods and code bases, to find out whether the methods have been getting too long. Most of the responses there suggested that, beyond maintenance on the method currently being edited, programmers don't, in general, keep an eye on the rest of the code base. So I thought I'd ask the question in general: Is code maintenance, in general, considered part of your daily work? Do you find that you're spending at least some of your time cleaning up, refactoring, rewriting code in the code base, to improve it, as part of your other assigned work? Is it expected of you/do you expect it of your teammates? Or is it more common to find that cleanup, refactoring, and general maintenance on the codebase as a whole, occurs in bursts (for example, mostly as part of code reviews, or as part of refactoring/cleaning up projects)?

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  • C# 4.0: Named And Optional Arguments

    - by Paulo Morgado
    As part of the co-evolution effort of C# and Visual Basic, C# 4.0 introduces Named and Optional Arguments. First of all, let’s clarify what are arguments and parameters: Method definition parameters are the input variables of the method. Method call arguments are the values provided to the method parameters. In fact, the C# Language Specification states the following on §7.5: The argument list (§7.5.1) of a function member invocation provides actual values or variable references for the parameters of the function member. Given the above definitions, we can state that: Parameters have always been named and still are. Parameters have never been optional and still aren’t. Named Arguments Until now, the way the C# compiler matched method call definition arguments with method parameters was by position. The first argument provides the value for the first parameter, the second argument provides the value for the second parameter, and so on and so on, regardless of the name of the parameters. If a parameter was missing a corresponding argument to provide its value, the compiler would emit a compilation error. For this call: Greeting("Mr.", "Morgado", 42); this method: public void Greeting(string title, string name, int age) will receive as parameters: title: “Mr.” name: “Morgado” age: 42 What this new feature allows is to use the names of the parameters to identify the corresponding arguments in the form: name:value Not all arguments in the argument list must be named. However, all named arguments must be at the end of the argument list. The matching between arguments (and the evaluation of its value) and parameters will be done first by name for the named arguments and than by position for the unnamed arguments. This means that, for this method definition: public static void Method(int first, int second, int third) this call declaration: int i = 0; Method(i, third: i++, second: ++i); will have this code generated by the compiler: int i = 0; int CS$0$0000 = i++; int CS$0$0001 = ++i; Method(i, CS$0$0001, CS$0$0000); which will give the method the following parameter values: first: 2 second: 2 third: 0 Notice the variable names. Although invalid being invalid C# identifiers, they are valid .NET identifiers and thus avoiding collision between user written and compiler generated code. Besides allowing to re-order of the argument list, this feature is very useful for auto-documenting the code, for example, when the argument list is very long or not clear, from the call site, what the arguments are. Optional Arguments Parameters can now have default values: public static void Method(int first, int second = 2, int third = 3) Parameters with default values must be the last in the parameter list and its value is used as the value of the parameter if the corresponding argument is missing from the method call declaration. For this call declaration: int i = 0; Method(i, third: ++i); will have this code generated by the compiler: int i = 0; int CS$0$0000 = ++i; Method(i, 2, CS$0$0000); which will give the method the following parameter values: first: 1 second: 2 third: 1 Because, when method parameters have default values, arguments can be omitted from the call declaration, this might seem like method overloading or a good replacement for it, but it isn’t. Although methods like this: public static StreamReader OpenTextFile( string path, Encoding encoding = null, bool detectEncoding = true, int bufferSize = 1024) allow to have its calls written like this: OpenTextFile("foo.txt", Encoding.UTF8); OpenTextFile("foo.txt", Encoding.UTF8, bufferSize: 4096); OpenTextFile( bufferSize: 4096, path: "foo.txt", detectEncoding: false); The complier handles default values like constant fields taking the value and useing it instead of a reference to the value. So, like with constant fields, methods with parameters with default values are exposed publicly (and remember that internal members might be publicly accessible – InternalsVisibleToAttribute). If such methods are publicly accessible and used by another assembly, those values will be hard coded in the calling code and, if the called assembly has its default values changed, they won’t be assumed by already compiled code. At the first glance, I though that using optional arguments for “bad” written code was great, but the ability to write code like that was just pure evil. But than I realized that, since I use private constant fields, it’s OK to use default parameter values on privately accessed methods.

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