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  • My integer overfloweth

    - by darcy
    While certain classes like java.lang.Integer and java.lang.Math have been in the platform since the beginning, that doesn't mean there aren't more enhancements to be made in such places! For example, earlier in JDK 8, library support was added for unsigned integer arithmetic. More recently, my colleague Roger Riggs pushed a changeset to support integer overflow, that is, to provide methods which throw an ArithmeticException on overflow instead of returning a wrapped result. Besides being helpful for various programming tasks in Java, methods like the those for integer overflow can be used to implement runtimes supporting other languages, as has been requested at a past JVM language summit. This year's language summit is coming up in July and I hope to get some additional suggestions there for helpful library additions as part of the general discussions of the JVM and Java libraries as a platform.

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  • Pathfinding library

    - by Shivan Dragon
    I'm an amateur game developer and somewhat amateur Java developer as well. I'm trying to find a way to have path finding for my game(s). I've first Googled for some existing Java libraries that have various path-finding implementations, but I've failed to find any. It seems to me that the only way to get pathfinding code is to use it via a game engine (like Unity). But I'd just like to have a library that I can use and make the game loop and other stuff on my own. Failing to find such a library I've tried implementing some algorithms myself. I've managed to make a running A* in Java, but for fancier stuff like D* I find it hard to do it by hand. So then, my question is, are there any Java libraries that contain at least some basic pathfinding algorithms implementations?

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  • Implementing separation of concerns via MVC

    - by user2368481
    I'm creating a question to see if my understanding of MVC separation is correct, I haven't been able to find a clear answer anywhere online. So is this the right way to implement it (in Java): I would have 3 .java files, one each for Model, Controller, View. I would put all the classes related to Model in the Model.java like so: //Model.java { public class Model //class fields public Model(); public ModelClassA(); public ModelClassB(); public ModelClassC(); } With the ModelClasses being any class that I consider belonging to the Model. Is it correct to have the classes within the Model Class, as I have read that nested classes should be avoided where possible.

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  • IDC and Becham Research: New analyst reports and webcast

    - by terrencebarr
    Embedded Java is getting a lot of attention in the analyst community these days. Check out these new analyst reports and a webcast by IDC as well as Beecham Research. IDC published a White Paper titled “Ghost in the Machine: Java for Embedded Development”, and an accompanying webcast recording. Highlights of the White Paper: The embedded systems industry is projected to continue to expand rapidly, reaching $2.1 trillion in 2015 The market for intelligent systems, where Java’s rich set of services are most needed, is projected to grow to 78% of all embedded systems in 2015  Java is widely used in embedded systems and is expected to continue to gain traction in areas where devices present an application platform for developers The free IDC webcast and White Paper can be accessed here. Beecham Research published a report titled “Designing an M2M Platform for the Connected World”. Highlights of the report: The total revenue for M2M Services is projected to double, from almost $15 billion in 2012 to over $30 billion in 2016 The primary driver for M2M solutions is now enabling new services Important trends that are developing are: Enterprise integration – more data and using the data more strategically, new markets in the Internet of Things (IoT), processing large amounts of data in real time (complex event processing) Using the same software development environment for all parts of an M2M solution is a major advantage if the software can be optimized for each part of the solution The free Beecham Research report can be accessed here. Cheers, – Terrence Filed under: Mobile & Embedded Tagged: iot, Java Embedded, M2M, research, webcast

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  • IDC and Becham Research: New analyst reports and webcast

    - by terrencebarr
    Embedded Java is getting a lot of attention in the analyst community these days. Check out these new analyst reports and a webcast by IDC as well as Beecham Research. IDC published a White Paper titled “Ghost in the Machine: Java for Embedded Development”, and an accompanying webcast recording. Highlights of the White Paper: The embedded systems industry is projected to continue to expand rapidly, reaching $2.1 trillion in 2015 The market for intelligent systems, where Java’s rich set of services are most needed, is projected to grow to 78% of all embedded systems in 2015  Java is widely used in embedded systems and is expected to continue to gain traction in areas where devices present an application platform for developers The free IDC webcast and White Paper can be accessed here. Beecham Research published a report titled “Designing an M2M Platform for the Connected World”. Highlights of the report: The total revenue for M2M Services is projected to double, from almost $15 billion in 2012 to over $30 billion in 2016 The primary driver for M2M solutions is now enabling new services Important trends that are developing are: Enterprise integration – more data and using the data more strategically, new markets in the Internet of Things (IoT), processing large amounts of data in real time (complex event processing) Using the same software development environment for all parts of an M2M solution is a major advantage if the software can be optimized for each part of the solution The free Beecham Research report can be accessed here. Cheers, – Terrence Filed under: Mobile & Embedded Tagged: iot, Java Embedded, M2M, research, webcast

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  • How fast does a language get outdated?

    - by Dummy Derp
    I started learning Java recently. I started learning it using books that I picked up from the library, some that I bought, and here and there from Java documentation. The book that I use for Java was published in the year 2011. In 2012, Java8 will be released followed by Java9 in the year 2013. The questions are: How do I keep myself updated about developments in Java without having to buy a tome for Java8 and/or Java9 Is a book published in 2008 an outdated book for studying JSP and Servelets? I'm talking about Head First Servlets and JSP

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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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  • Eclipse no longer useful

    - by dgood1
    When I got my Eclipse from the Ubuntu Software Center, it was good and worked fine. I could work on Java projects fine. This week I was required to add ADT and tried the ADT-bundle, assuming it had everthing I needed, seeing that the SDK had more steps. So now, I can create Android apps using the ADT-bundle. I tried to work on my java projects again and I now discovered: I can't run my java projects: "The selection cannot be launched. And there are no recent launches." error. I also believe Eclipse doesn't know it's a java program because it all in black and white. Not the usual green/blue/red/black things when making comments, variables and Strings. I can't make new projects of ANYTHING unless I use the adt-bundle. New project only offers CVS (whatever that is) My perspectives seem limited. I remembered more choices and now I'm limited to [Java], Resource, CVS Repository, debug, Team Sync. I was told to be able to use perspectives to swap between Android and Java developing. Even after the ADT installation using "Install new Software",nothing. I can't uninstall/purge/remove Eclipse via the terminal. I tried removing it then reinstalling it via the Ubuntu Software Cetner. No results other than it's temporary removal. (Possibly unrelated) A large number of repositories are not found when updating Eclipse. (See Step 8 in Summary of what I did...) Although, on checking the versions and installation history, I confirmed Android and Java are installed. It probably just doesn't know it's there. Eclipse Indigo: Version: 3.7.2 Build id: I20110613-1736 Summary of what I did before and during the problem: Downloaded adt-bundle. Attempted instructions from teacher. (Install new Software) (Failed but other than an annoying "can't find repository" during each update, no damage to report) (Fixed) Ran "eclipse" executable from the adt-bundle. Updated Eclipse. (After restart, I noticed the problem) NOTE: other than window arrangement, I had no customizations. Played around with the Windowspreferences and Projectpropertied. Restored to default settings after no results. Tried "apt-get purge eclipse". Couldn't find Eclipse so, nothing happened. Used Software center. No results. Tried swapping workspaces. I tried different folder, deeper folder, renaming. All return the same problem. Deleted adt-bundle (browsed folders then delete). Got Adt-sdk only. Installed. Can't find any changes other than some disk space usage. Of course, I can't make Android apps until I unzip the bundle again. WindowsPreferencesInstall/UpdateAvailable Software Sites, Checked as many repositories as possible, then updated. Still nothing. I'm about to get a second try on uninstalling it, because I think my last action will just be taking up space. But I'll wait for tomorrow, in case the answer will help. Any thoughts?

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  • Why are most GNU's software written in C

    - by BallroomProgrammer
    I am a Java developer, and I rarely write GUI program in C. However, I noticed that many GNU's projects, such as PSPP, R, Dia, etc., are written in C, instead of Java or C++. I personally don't mind this, but I am really curious why GNU favors C so much. My understanding is that C is the one that supports the least in object-oriented programming, and today's CS education really emphasizes OOP, as OOP really makes codes more reusable. In this case, why would so many developers choose to develop in C instead of C++ or Java. Does anyone know why GNU's software are so exclusively written in C? Do you think or GNU's software should be written in C++ or Java so that the source code could be more useful to people? Why or why not?

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  • Why was Scala not implemented with C or C++

    - by jpartogi
    Does anybody know why was Scala implemented in Java and .NET instead of C or C++? Most languages are implemented with Cor C++ [i.e Erlang, Python, PHP, Ruby, Perl]. What are the advantages for Scala implemented in Java and .NET other than giving access to Java and .NET libraries? UPDATE Woudln't Scala gain more benefit if it is implemented in C because it can be tuned better rather than relying on JVM?

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  • Purpose of "new" keyword

    - by Channel72
    The new keyword in languages like Java, Javascript, and C# creates a new instance of a class. This syntax seems to have been inherited from C++, where new is used specifically to allocate a new instance of a class on the heap, and return a pointer to the new instance. In C++, this is not the only way to construct an object. You can also construct an object on the stack, without using new - and in fact, this way of constructing objects is much more common in C++. So, coming from a C++ background, the new keyword in languages like Java, Javascript, and C# seemed natural and obvious to me. Then I started to learn Python, which doesn't have the new keyword. In Python, an instance is constructed simply by calling the constructor, like: f = Foo() At first, this seemed a bit off to me, until it occurred to me that there's no reason for Python to have new, because everything is an object so there's no need to disambiguate between various constructor syntaxes. But then I thought - what's really the point of new in Java? Why should we say Object o = new Object();? Why not just Object o = Object();? In C++ there's definitely a need for new, since we need to distinguish between allocating on the heap and allocating on the stack, but in Java all objects are constructed on the heap, so why even have the new keyword? The same question could be asked for Javascript. In C#, which I'm much less familiar with, I think new may have some purpose in terms of distinguishing between object types and value types, but I'm not sure. Regardless, it seems to me that many languages which came after C++ simply "inherited" the new keyword - without really needing it. It's almost like a vestigial keyword. We don't seem to need it for any reason, and yet it's there. Question: Am I correct about this? Or is there some compelling reason that new needs to be in C++-inspired memory-managed languages like Java, Javascript and C#?

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  • Which programming language to develop software for USC that also runs on other OS?? (WINDOWS/OSX)

    - by Marian Lux
    I have skills in JAVA and C#: First i had a closer look to JAVA (Eclipse with Windowbuilder-Plugin) - Swing: But there is no natvie GUI-Support for GTK3 (e.g., HUD seems not to work) Then i was at JAVA - SWT: It is to heavy. I want do code a small app that improves the Ubuntu desktop. I don't want to ship a program with eclipse included. After that i found C# Mono (Monodevelop): GTK-shparp is only for GTK2 available. A GTK3-port will come soon but is it possible to convert the program from GTK2 to GTK3 without extra adaptations? The next bad thing is, that MONO is now dropped from Ubuntu LTS 12.04. So i have no chance that my app would be a default-app in an Ubuntu-Image. (This is also a factor for me to choose a programming language). I know there are other techs but i want to use as programing language JAVA or C#.

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  • Frames per Second and Updates per Second [on hold]

    - by matt murray
    So this is more a general resources question, as I am seeking knowledge on how best to conserve resources in a game (I am writing in Java, and please this is not a thread on what language I should write it in, I have already chosen Java) so that the updates and frames per second could be the highest they could be. In general I am just searching for any articles you may have, any personal experience, anything what so ever that could be of use to a pretty new Java game developer on the subject! Thanks in advance!

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  • Why isn't reflection on the SCJP / OCJP?

    - by Nick Rosencrantz
    I read through Kathy Sierra's SCJP study guide and I will read it again more throughly to improve myself as a Java programmer and be able to take the certification either Java 6 or wait for the Java 7 exam (I'm already employed as Java developer so I'm in no hurry to take the exam.) Now I wonder why reflection is not on the exam? The book it seems covers everything that should be on the exam and AFAIK reflection is at least as important as threads if not more used inpractice since many frameworks use reflection. Do you know why reflection is not part of the SCJP? Do you agree that it's at least important to know reflection as threads? Thanks for any answer

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  • creating a pre-menu level select screen

    - by Ephiras
    Hi I am working on creating a tower Defence java applet game and have come to a road block about implementing a title screen that i can select the level and difficulty of the rest of the game. my title screen class is called Menu. from this menu class i need to pass in many different variables into my Main class. i have used different classes before and know how to run them and such. but if both classes extend applet and each has its individual graphics method how can i run things from Main even though it was created in Menu. what i essentially want to do is run the Menu class withits action listeners and graphics until a Difficulty button has been selected, run the main class (which 100% works without having to have the Menu class) and pretty much terminate Menu so that i cannot go back to it, do not see its buttons or graphics menus. can i run one applet annd when i choose a button close that one and launch the other one? IF you would like to download the full project you can find it here, i had to comment out all the code that wasn't working my Menu class import java.awt.*; import java.awt.event.*; import java.applet.*; public class Menu extends Applet implements ActionListener{ Button bEasy,bMed,bHard; Main m; public void init(){ bEasy= new Button("Easy"); bEasy.setBounds(140,200,100,50); add(bEasy); bMed = new Button("Medium");bMed.setBounds(280,200,100,50); add(bMed); bHard= new Button("Hard");bHard.setBounds(420,200,100,50); add(bHard); setLayout(null); } public void actionPerformed(ActionEvent e){ Main m = new Main(20,10,3000,mapMed);//break; switch (e.getSource()){ case bEasy: Main m = new Main(6000,20,"levels/levelEasy.png");break;//enimies tower money world case bMed: Main m = new Main(4000,15,"levels/levelMed.png");break; case bHard: Main m = new Main(2000,10,"levels/levelEasy.png");break; default: break; } } public void paint(){ //m.draw(g) } } and here is my main class initialising code. import java.awt.*; import java.awt.event.*; import java.applet.*; import java.io.IOException; public class Main extends Applet implements Runnable, MouseListener, MouseMotionListener, ActionListener{ Button startButton, UpgRange, UpgDamage; //set up the buttons Color roadCol,startCol,finCol,selGrass,selRoad; //set up the colors Enemy e[][]; Tower t[]; Image towerpic,backpic,roadpic,levelPic; private Image i; private Graphics doubleG; //here is the world 0=grass 1=road 2=start 3=end int world[][],eStartX,eStartY; boolean drawMouse,gameEnd; static boolean start=false; static int gridLength=15; static int round=0; int Mx,My,timer=1500; static int sqrSize=31; int towers=0,towerSelected=-10; static int castleHealth=2000; String levelPath; //choose the level Easy Med or Hard int maxEnemy[] = {5,7,12,20,30,15,50,30,40,60};//number of enimies per round int maxTowers=15;//maximum number of towers allowed static int money =2000,damPrice=600,ranPrice=350,towerPrice=700; //money = the intial ammount of money you start of with //damPrice is the price to increase the damage of a tower //ranPrice is the price to increase the range of a tower public void main(int cH,int mT,int mo,int dP,int rP,int tP,String path,int[] mE)//constructor 1 castleHealth=cH; maxTowers=mT; money=mo; damPrice=dP; ranPrice=rP; towerPrice=tP; String levelPath=path; maxEnemy = mE; buildLevel(); } public void main(int cH,int mT,String path)//basic constructor castleHealth=cH; maxTowers=mT; String levelPath=path; maxEnemy = mE; buildLevel(); } public void init(){ setSize(sqrSize*15+200,sqrSize*15);//set the size of the screen roadCol = new Color(255,216,0);//set the colors for the different objects startCol = new Color(0,38,255); finCol = new Color(255,0,0); selRoad = new Color(242,204,155);//selColor is the color of something when your mouse hovers over it selGrass = new Color(0,190,0); roadpic = getImage(getDocumentBase(),"images/road.jpg"); towerpic = getImage(getDocumentBase(),"images/tower.png"); backpic = getImage(getDocumentBase(),"images/grass.jpg"); levelPic = getImage(getDocumentBase(),"images/level.jpg"); e= new Enemy[maxEnemy.length][];//activates all of the enimies for (int r=0;r<e.length;r++) e[r] = new Enemy[maxEnemy[r]]; t= new Tower[maxTowers]; for (int i=0;i<t.length;i++) t[i]= new Tower();//activates all the towers for (int i=0;i<e.length; i++)//sets all of the enimies starting co ordinates for (int j=0;j<e[i].length;j++) e[i][j] = new Enemy(eStartX,eStartY,world); initButtons();//initialise all the buttons addMouseMotionListener(this); addMouseListener(this); }

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  • Command line options style - POSIX or what?

    - by maaartinus
    Somewhere I saw a rant against java/javac allegedly using a mix of Windows and Unix style like java -classpath ... -ea ... Something IMHO, it is no mix, it's just like find works as well, isn't it? AFAIK, according to POSIX, the syntax should be like java --classpath ... --ea ... Something and -abcdef would mean specifying 6 short options at once. I wonder which version leads in general to less typing and less errors. I'm writing a small utility in Java and in no case I'm going to use Windows style /a /b since I'm interested primarily in Unix. What style should I choose?

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  • Android Game Development problem with Speed = Distance / Time

    - by Charlton Santana
    I have been coding speed for an object. I have made it so the object will move from one end of the screen to another at a speed depending on the screen size, at the monemt I have made it so it will take one second to pass the screen. So i have worked out the speed in code but when I go to assign the speed it tells me to force close and i do not understand why. Here is the code: MainGame Code: @Override protected void onDraw(Canvas canvas) { setBlockSpeed(getWidth()); } private int blockSpeed; private void setBlockSpeed(int screenWidth){ Log.d(TAG, "screenWidth " + screenWidth); blockSpeed = screenWidth / 100; // 100 is the FPS.. i want it to take 1 second to pass the screen Math.round(blockSpeed); // to make it a whole number block.speed = blockSpeed; // this is line 318!! if i put eg block.speed = 8; it still tells me to force close } Block.java Code: public int speed; public void draw(Canvas canvas) { canvas.drawBitmap(bitmap, x - (bitmap.getWidth() / 2), y - (bitmap.getHeight() / 2), null); if(dontmove == 0){ this.x -= speed; // if it was eg this.x -= 18; it would not have an error } } The exception 06-08 13:22:34.315: E/AndroidRuntime(2801): FATAL EXCEPTION: Thread-11 06-08 13:22:34.315: E/AndroidRuntime(2801): java.lang.NullPointerException 06-08 13:22:34.315: E/AndroidRuntime(2801): at com.charltonsantana.game.MainGame.setBlockSpeed(MainGame.java:318) 06-08 13:22:34.315: E/AndroidRuntime(2801): at com.charltonsantana.game.MainGame.onDraw(MainGame.java:351) 06-08 13:22:34.315: E/AndroidRuntime(2801): at com.charltonsantana.game.MainThread.run(MainThread.java:64)

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  • the OpenJDK group at Oracle is growing

    - by john.rose
    p.p1 {margin: 0.0px 0.0px 12.0px 0.0px; font: 12.0px Times} span.s1 {text-decoration: underline ; color: #0000ee} The OpenJDK software development team at Oracle is hiring. To get an idea of what we’re looking for, go to the Oracle recruitment portal and enter the Keywords “Java Platform Group” and the Location Keywords “Santa Clara”.  (We are a global engineering group based in Santa Clara.)  It’s pretty obvious what we are working on; just dive into a public OpenJDK repository or OpenJDK mailing list. Here is a typical job description from the current crop of requisitions: The Java Platform group is looking for an experienced, passionate and highly-motivated Software Engineer to join our world class development effort. Our team is responsible for delivering the Java Virtual Machine that is used by millions of developers. We are looking for a development engineer with a strong technical background and thorough understanding of the Java Virtual Machine, Java execution runtime, classloading, garbage collection, JIT compiler, serviceability and a desire to drive innovations. As a member of the software engineering division, you will take an active role in the definition and evolution of standard practices and procedures. You will be responsible for defining and developing software for tasks associated with the developing, designing and debugging of software applications or operating systems. Work is non-routine and very complex, involving the application of advanced technical/business skills in area of specialization. Leading contributor individually and as a team member, providing direction and mentoring to others. BS or MS degree or equivalent experience relevant to functional area. 7 years of software engineering or related experience.

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  • javaws crashes, error in ld-linux-x86-64.so.2

    - by user54214
    I am running Ubuntu 11.10 64 bit client as Dom0 and Xen. I am having problems getting java up and running. Java itself seems to work fine, however I get strange errors, for example when I start javaws. I tried different versions and always get the same errors. I tried openjdk 1.6 and 1.7 as well as sunjava6 and 7. I alway get an error in the same lib All other applications are working fine, so it seems ld-linux-x86-64.so.2 is working fine. Any hints what could be wrong? Ubuntu01:~$ javaws # # A fatal error has been detected by the Java Runtime Environment: # # SIGILL (0x4) at pc=0x00007f4e74c5ad10, pid=7974, tid=139974945277696 # # JRE version: 6.0_23-b23 # Java VM: OpenJDK 64-Bit Server VM (20.0-b11 mixed mode linux-amd64 compressedoops) # Derivative: IcedTea6 1.11pre # Distribution: Ubuntu 11.10, package 6b23~pre11-0ubuntu1.11.10.2 # Problematic frame: # C [ld-linux-x86-64.so.2+0x14d10] _dl_make_stack_executable+0x2b70 # # An error report file with more information is saved as: # /home/r/hs_err_pid7974.log # # If you would like to submit a bug report, please include # instructions how to reproduce the bug and visit: # https://bugs.launchpad.net/ubuntu/+source/openjdk-6/ # The crash happened outside the Java Virtual Machine in native code. # See problematic frame for where to report the bug. # Aborted

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  • install matlab 2013a with error

    - by user158449
    I tried to install Matlab2013a in my laptop (Ubuntu system). I download a ISO file (very big) and followed their instruction: mount it and run "install". But it returns me an error: Cannot locate Java Runtime Enviroment (JRE). The directory ~/Matlab/sys/java/jre/glnx86/jre does not exist. In the folder ~/Matlab/sys/java/jre/, what I have is "glnxa64". Does that mean that I can't install this version of Matlab in my 32bit laptop? This java comes from Matlab. How should I get it work?

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  • Prevent APT from overwriting JCE jars

    - by Doc
    My server runs a Java application that requires I replace a few java library files with ones I downloaded on my own. This has to do with JCE security extensions and isn't really relevant to my question. I've found that these library files tend to get overwritten by apt when it later updates my java package. Is there a apt-friendly way of masking these specific files so apt won't touch them? Potential Solutions I'm considering just removing the write flag from the files, though I'm expecting this will cause apt to spew its guts everywhere when it later tries to overwrite them? Perhaps there's a java custom library directory I don't know of, where I can park my files and they'll be loaded instead of the package's defaults? The last-resort option I'm considering is writing a cron job to periodically replace the files with my versions. I hate this option.

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  • See you at OSCON!

    - by darcy
    In just under a month, I'll be speaking at the OSCON Java conference about various OpenJDK and JDK 7 matters: JDK 7 in a Nutshell The State of JDK and OpenJDK More detailed talks on those topics include Stuart's session on Coin in Action: Using New Java SE 7 Language Features in Real Code and Dalibor's OpenJDK – When And How To Contribute To The Java SE Reference Implementation. See you in Portland!

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  • Eclipse not launching

    - by user274959
    I have installed Ubuntu 14.04, I have installed Eclipse using Ubuntu Software Center. But Eclipse is not opening, when I click it is not opening or showing any error message it is very silent. Output for java -version: java version "1.7.0_55" Java(TM) SE Runtime Environment (build 1.7.0_55-b13) Java HotSpot(TM) Server VM (build 24.55-b03, mixed mode) uname -a: Linux Lenovo-IdeaPad-Z510 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:08:14 UTC 2014 i686 i686 i686 GNU/Linux When I give Eclipse in terminal I am getting The program 'eclipse' is currently not installed. You can install it by typing: sudo apt-get install eclipse-platform And when I give sudo apt-get install eclipse-platform Reading package lists... Done Building dependency tree Reading state information... Done eclipse-platform is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.

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  • Why do memory-managed languages retain the `new` keyword?

    - by Channel72
    The new keyword in languages like Java, Javascript, and C# creates a new instance of a class. This syntax seems to have been inherited from C++, where new is used specifically to allocate a new instance of a class on the heap, and return a pointer to the new instance. In C++, this is not the only way to construct an object. You can also construct an object on the stack, without using new - and in fact, this way of constructing objects is much more common in C++. So, coming from a C++ background, the new keyword in languages like Java, Javascript, and C# seemed natural and obvious to me. Then I started to learn Python, which doesn't have the new keyword. In Python, an instance is constructed simply by calling the constructor, like: f = Foo() At first, this seemed a bit off to me, until it occurred to me that there's no reason for Python to have new, because everything is an object so there's no need to disambiguate between various constructor syntaxes. But then I thought - what's really the point of new in Java? Why should we say Object o = new Object();? Why not just Object o = Object();? In C++ there's definitely a need for new, since we need to distinguish between allocating on the heap and allocating on the stack, but in Java all objects are constructed on the heap, so why even have the new keyword? The same question could be asked for Javascript. In C#, which I'm much less familiar with, I think new may have some purpose in terms of distinguishing between object types and value types, but I'm not sure. Regardless, it seems to me that many languages which came after C++ simply "inherited" the new keyword - without really needing it. It's almost like a vestigial keyword. We don't seem to need it for any reason, and yet it's there. Question: Am I correct about this? Or is there some compelling reason that new needs to be in C++-inspired memory-managed languages like Java, Javascript and C#?

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  • Too much to learn, so little time

    - by Phobia
    Okay, so I'm a java developer (or at least I think I am),and also a student at the same time I want to get a job when I graduate,I'll be graduating in a year or so (hopefully) (Note: my major has nothing to do with programming) Now, I'm between a rock and a hard place I also want to nail the foundations to become a good software developer. I want to be able to write programs that solve problems,not just glue code The software market in my country for java developers is just a few developers working with Java EE (struts,spring,hibernate....etc) I'm currently learning C++ with this book. I've also watched most of the 1st lecture of this course and I understood pretty much everything I watched To sum it up, I have three options Learn Java EE Learn C++ Learn Scheme Which is better for me at this point?

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