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  • IP assignment in a /28 block

    - by mks
    Need help on setting up firewall router. My config is as below: Public static network ID: x.x.x.48/28 gateway: x.x.x.49 available IP for the hosts: x.x.x.52 to 62 gw_eth0 <-- fw_eth0 - fw_eth1 <-- dmz_switch Four servers are connected on dmz_switch (say s1, s2, s3, s4) all have to use public static IP address from the above block. Any recommendation on IP assignment and route setup? Do I need to subnet the above block further or simply use /32 netmask and point-to-point static routes in the above setup?

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  • When to use mixins in Ruby

    - by Gilles
    I am wondering when to use mixins? I have read about them. Many authors compare them to interfaces, abstract classes, etc. Mixins are modules that are mixed-in and modules are a way to group similar methods, constants and classes together. I have seen examples where a module for math functions is created. It makes sense to group and reuse such functions but should I only mix these in a class if I am faced with an inheritance situation? Should I mix these in anytime I want to use them in a class? Should they be used exactly like interfaces in other languages or are there other subtleties?

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  • Switching from abstract class to interface

    - by nischayn22
    I have an abstract class which has all abstract methods except one which constructs objects of the subclasses. Now my mentor asked me to move this abstract class to an interface. Having an interface is no problem except with the method used to construct subclass objects. Where should this method go now? Also, I read somewhere that interfaces are more efficient than abstract classes. Is this true? Here's an example of my classes abstract class Animal { //many abstract methods getAnimalobject(some parameter) { return //appropriate subclass } } class Dog extends Animal {} class Elephant extends Animal {}

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  • Taming Hopping Windows

    - by Roman Schindlauer
    At first glance, hopping windows seem fairly innocuous and obvious. They organize events into windows with a simple periodic definition: the windows have some duration d (e.g. a window covers 5 second time intervals), an interval or period p (e.g. a new window starts every 2 seconds) and an alignment a (e.g. one of those windows starts at 12:00 PM on March 15, 2012 UTC). var wins = xs     .HoppingWindow(TimeSpan.FromSeconds(5),                    TimeSpan.FromSeconds(2),                    new DateTime(2012, 3, 15, 12, 0, 0, DateTimeKind.Utc)); Logically, there is a window with start time a + np and end time a + np + d for every integer n. That’s a lot of windows. So why doesn’t the following query (always) blow up? var query = wins.Select(win => win.Count()); A few users have asked why StreamInsight doesn’t produce output for empty windows. Primarily it’s because there is an infinite number of empty windows! (Actually, StreamInsight uses DateTimeOffset.MaxValue to approximate “the end of time” and DateTimeOffset.MinValue to approximate “the beginning of time”, so the number of windows is lower in practice.) That was the good news. Now the bad news. Events also have duration. Consider the following simple input: var xs = this.Application                 .DefineEnumerable(() => new[]                     { EdgeEvent.CreateStart(DateTimeOffset.UtcNow, 0) })                 .ToStreamable(AdvanceTimeSettings.IncreasingStartTime); Because the event has no explicit end edge, it lasts until the end of time. So there are lots of non-empty windows if we apply a hopping window to that single event! For this reason, we need to be careful with hopping window queries in StreamInsight. Or we can switch to a custom implementation of hopping windows that doesn’t suffer from this shortcoming. The alternate window implementation produces output only when the input changes. We start by breaking up the timeline into non-overlapping intervals assigned to each window. In figure 1, six hopping windows (“Windows”) are assigned to six intervals (“Assignments”) in the timeline. Next we take input events (“Events”) and alter their lifetimes (“Altered Events”) so that they cover the intervals of the windows they intersect. In figure 1, you can see that the first event e1 intersects windows w1 and w2 so it is adjusted to cover assignments a1 and a2. Finally, we can use snapshot windows (“Snapshots”) to produce output for the hopping windows. Notice however that instead of having six windows generating output, we have only four. The first and second snapshots correspond to the first and second hopping windows. The remaining snapshots however cover two hopping windows each! While in this example we saved only two events, the savings can be more significant when the ratio of event duration to window duration is higher. Figure 1: Timeline The implementation of this strategy is straightforward. We need to set the start times of events to the start time of the interval assigned to the earliest window including the start time. Similarly, we need to modify the end times of events to the end time of the interval assigned to the latest window including the end time. The following snap-to-boundary function that rounds a timestamp value t down to the nearest value t' <= t such that t' is a + np for some integer n will be useful. For convenience, we will represent both DateTime and TimeSpan values using long ticks: static long SnapToBoundary(long t, long a, long p) {     return t - ((t - a) % p) - (t > a ? 0L : p); } How do we find the earliest window including the start time for an event? It’s the window following the last window that does not include the start time assuming that there are no gaps in the windows (i.e. duration < interval), and limitation of this solution. To find the end time of that antecedent window, we need to know the alignment of window ends: long e = a + (d % p); Using the window end alignment, we are finally ready to describe the start time selector: static long AdjustStartTime(long t, long e, long p) {     return SnapToBoundary(t, e, p) + p; } To find the latest window including the end time for an event, we look for the last window start time (non-inclusive): public static long AdjustEndTime(long t, long a, long d, long p) {     return SnapToBoundary(t - 1, a, p) + p + d; } Bringing it together, we can define the translation from events to ‘altered events’ as in Figure 1: public static IQStreamable<T> SnapToWindowIntervals<T>(IQStreamable<T> source, TimeSpan duration, TimeSpan interval, DateTime alignment) {     if (source == null) throw new ArgumentNullException("source");     // reason about DateTime and TimeSpan in ticks     long d = Math.Min(DateTime.MaxValue.Ticks, duration.Ticks);     long p = Math.Min(DateTime.MaxValue.Ticks, Math.Abs(interval.Ticks));     // set alignment to earliest possible window     var a = alignment.ToUniversalTime().Ticks % p;     // verify constraints of this solution     if (d <= 0L) { throw new ArgumentOutOfRangeException("duration"); }     if (p == 0L || p > d) { throw new ArgumentOutOfRangeException("interval"); }     // find the alignment of window ends     long e = a + (d % p);     return source.AlterEventLifetime(         evt => ToDateTime(AdjustStartTime(evt.StartTime.ToUniversalTime().Ticks, e, p)),         evt => ToDateTime(AdjustEndTime(evt.EndTime.ToUniversalTime().Ticks, a, d, p)) -             ToDateTime(AdjustStartTime(evt.StartTime.ToUniversalTime().Ticks, e, p))); } public static DateTime ToDateTime(long ticks) {     // just snap to min or max value rather than under/overflowing     return ticks < DateTime.MinValue.Ticks         ? new DateTime(DateTime.MinValue.Ticks, DateTimeKind.Utc)         : ticks > DateTime.MaxValue.Ticks         ? new DateTime(DateTime.MaxValue.Ticks, DateTimeKind.Utc)         : new DateTime(ticks, DateTimeKind.Utc); } Finally, we can describe our custom hopping window operator: public static IQWindowedStreamable<T> HoppingWindow2<T>(     IQStreamable<T> source,     TimeSpan duration,     TimeSpan interval,     DateTime alignment) {     if (source == null) { throw new ArgumentNullException("source"); }     return SnapToWindowIntervals(source, duration, interval, alignment).SnapshotWindow(); } By switching from HoppingWindow to HoppingWindow2 in the following example, the query returns quickly rather than gobbling resources and ultimately failing! public void Main() {     var start = new DateTimeOffset(new DateTime(2012, 6, 28), TimeSpan.Zero);     var duration = TimeSpan.FromSeconds(5);     var interval = TimeSpan.FromSeconds(2);     var alignment = new DateTime(2012, 3, 15, 12, 0, 0, DateTimeKind.Utc);     var events = this.Application.DefineEnumerable(() => new[]     {         EdgeEvent.CreateStart(start.AddSeconds(0), "e0"),         EdgeEvent.CreateStart(start.AddSeconds(1), "e1"),         EdgeEvent.CreateEnd(start.AddSeconds(1), start.AddSeconds(2), "e1"),         EdgeEvent.CreateStart(start.AddSeconds(3), "e2"),         EdgeEvent.CreateStart(start.AddSeconds(9), "e3"),         EdgeEvent.CreateEnd(start.AddSeconds(3), start.AddSeconds(10), "e2"),         EdgeEvent.CreateEnd(start.AddSeconds(9), start.AddSeconds(10), "e3"),     }).ToStreamable(AdvanceTimeSettings.IncreasingStartTime);     var adjustedEvents = SnapToWindowIntervals(events, duration, interval, alignment);     var query = from win in HoppingWindow2(events, duration, interval, alignment)                 select win.Count();     DisplayResults(adjustedEvents, "Adjusted Events");     DisplayResults(query, "Query"); } As you can see, instead of producing a massive number of windows for the open start edge e0, a single window is emitted from 12:00:15 AM until the end of time: Adjusted Events StartTime EndTime Payload 6/28/2012 12:00:01 AM 12/31/9999 11:59:59 PM e0 6/28/2012 12:00:03 AM 6/28/2012 12:00:07 AM e1 6/28/2012 12:00:05 AM 6/28/2012 12:00:15 AM e2 6/28/2012 12:00:11 AM 6/28/2012 12:00:15 AM e3 Query StartTime EndTime Payload 6/28/2012 12:00:01 AM 6/28/2012 12:00:03 AM 1 6/28/2012 12:00:03 AM 6/28/2012 12:00:05 AM 2 6/28/2012 12:00:05 AM 6/28/2012 12:00:07 AM 3 6/28/2012 12:00:07 AM 6/28/2012 12:00:11 AM 2 6/28/2012 12:00:11 AM 6/28/2012 12:00:15 AM 3 6/28/2012 12:00:15 AM 12/31/9999 11:59:59 PM 1 Regards, The StreamInsight Team

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  • Which programming career path fits my terms? [closed]

    - by Goward Gerald
    I am sick and tired of my enterprise development job, I need some programming direction like this: Demanded in jobs-market Demanded in freelance market Can use Ubuntu as development environment Not enterprise. Standalone, mobile, web-development, anything, just not enterprise. Basically, I need a programming direction which doesn't need 20 developers, terribly big databases systems and long going projects with intense long-term support, I don't want enterprise job where a lot of people are working on one terribly big project and do modules to it all day long. Instead, I need something where: Projects change pretty often Projects are little, or medium-sized (in terms of code, modules and people working on it) but still not enterprise-sized Possible for freelance, solo-development, or at least requires a team of 3-4 programmers. Not like in enterprise where you feel like a drop in the sea with your 50 classes while system itself has hundreds of classes. Suggestions please?

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  • Running a compiled Java program

    - by Roshan George
    I have a question on a compiled Java program that I have written. I have a Java file that has three classes defined within it. When I compiled the program I got a total of four classes. How do I make this into a form where I can run my application just by clicking an icon or something, or by issuing just a single command. For example, if I make it as an exe file, it could run only on Windows, how do I make it into a form compatible with all Oses. And hoe?

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  • Serious Forum Design Issue

    - by John
    I want to launch a school forum for a country. I'm in dilemma as to how to design this forum. Country will have many states, each state will have cities, each city will have many schools. Each school will have many classes( 1st - 12th). It looks like this: States - Cities - Schools - Classes I want to make each class as forum. Now the biggest problems are two fold: If I were to list even 1000 schools it will create huge number of forums and I don't think forum softwares(PHPBB, MyBB) are designed to support these many Secondly creating and maintaining huge forums is also very difficult. Ideally I'd like to duplicate existing forum hierarchy to new one. I've done lot of search and I've found that such type of forums are infeasible and such designs don't work. Leave alone the fact the nobody uses such a forum. Keeping in mind this, how should I go about designing this forum?

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  • Are microsoft certificates useful [closed]

    - by grabah
    Possible Duplicate: Why should you get MCTS certified? Are microsoft certificates useful for anything more than beeing a bonus on job interviews? I do believe in formal training but i'm sceptical about their value, specialy if i dont' take classes (not enough time/money) but study at home/online and than go directly to take exams. Would you recomend taking preparation classes, or are they just waste of time? (or perhaps is whole certification thing waste of time?) (i have several years of expirience and currently working in software development)

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  • How to improve programming skills?

    - by Mike
    I'm very new to programming. I started learning PHP about half a year ago, so I do know something. I can write small functions, I can export and import information from a database and I can make a website. I don't know OOP principles and I don't know about objects and classes. Should I move to OOP principles and learn about classes, methods and objects? If not, what should I do? Continue writing simple code? How can a programmer write his/her own API? Is OOP necessary to do this? So how can i improve my skills? I love programming. I spend my 24/7 on it, so any help will be appreciated.

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  • C# 4.0 Optional/Named Parameters Beginner&rsquo;s Tutorial

    - by mbcrump
    One of the interesting features of C# 4.0 is for both named and optional arguments.  They are often very useful together, but are quite actually two different things.  Optional arguments gives us the ability to omit arguments to method invocations. Named arguments allows us to specify the arguments by name instead of by position.  Code using the named parameters are often more readable than code relying on argument position.  These features were long overdue, especially in regards to COM interop. Below, I have included some examples to help you understand them more in depth. Please remember to target the .NET 4 Framework when trying these samples. Code Snippet using System;   namespace ConsoleApplication3 {     class Program     {         static void Main(string[] args)         {               //C# 4.0 Optional/Named Parameters Tutorial               Foo();                              //Prints to the console | Return Nothing 0             Foo("Print Something");             //Prints to the console | Print Something 0             Foo("Print Something", 1);          //Prints to the console | Print Something 1             Foo(x: "Print Something", i: 5);    //Prints to the console | Print Something 5             Foo(i: 5, x: "Print Something");    //Prints to the console | Print Something 5             Foo("Print Something", i: 5);       //Prints to the console | Print Something 5             Foo2(i3: 77);                       //Prints to the console | 77         //  Foo(x:"Print Something", 5);        //Positional parameters must come before named arguments. This will error out.             Console.Read();         }           static void Foo(string x = "Return Nothing", int i = 0)         {             Console.WriteLine(x + " " + i + Environment.NewLine);         }           static void Foo2(int i = 1, int i2 = 2, int i3 = 3, int i4 = 4)         {             Console.WriteLine(i3);         }     } }

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  • Is encoding needed in this decryption?

    - by Lijo
    I have a Encryption – Decryption scenario as shown below. //[Clear text ID string as input] -- [(ASCII GetByte) + Encoding] -- [Encrption as byte array] -- [Database column is in VarBinary] -- [Pass byte[] as VarBinary parameter to SP for comparison] //[ID stored as VarBinary in Database] -- [Read as byte array] -- [(Decrypt as byte array) + Encoding + (ASCII Get String)] -- Show as string in the UI My question is in the decryption scenario. After decryption I get a byte array. I am doing an encoding (IBM037) after that. Is it correct? Is there something wrong in the flow shown above? private static byte[] GetEncryptedID(string id) { Interface_Request input = new Interface_Request(); input.RequestText = Encodeto64(id); input.RequestType = Encryption; ProgramInterface inputRequest = new ProgramInterface(); inputRequest.Test_Trial_Request = input; using (KTestService operation = new KTestService()) { return ((operation.KTrialOperation(inputRequest)).Test_Trial_Response.ResponseText); } } private static string GetDecryptedID(byte[] id) { Interface_Request input = new Interface_Request(); input.RequestText = id; input.RequestType = Decryption; ProgramInterface request = new ProgramInterface(); request.Test_Trial_Request = input; using (KTestService operationD = new KTestService()) { ProgramInterface1 response = operationD.KI014Operation(request); byte[] decryptedValue = response.ICSF_AES_Response.ResponseText; Encoding sourceByteFormat = Encoding.GetEncoding("IBM037"); Encoding destinationByteFormat = Encoding.ASCII; //Convert from one byte format to other (IBM to ASCII) byte[] ibmEncodedBytes = Encoding.Convert(sourceByteFormat, destinationByteFormat,decryptedValue); return System.Text.ASCIIEncoding.ASCII.GetString(ibmEncodedBytes); } } private static byte[] EncodeTo64(string toEncode) { byte[] dataInBytes = System.Text.ASCIIEncoding.ASCII.GetBytes(toEncode); Encoding destinationByteFormat = Encoding.GetEncoding("IBM037"); Encoding sourceByteFormat = Encoding.ASCII; //Convert from one byte format to other (ASCII to IBM) byte[] asciiBytes = Encoding.Convert(sourceByteFormat, destinationByteFormat, dataInBytes); return asciiBytes; }

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  • Can't serve files without extension because they "appear to be script" on IIS7.5

    - by madd0
    I created a certain number of static JSON files with no extension in a subfolder of my site. I want to use them for tests. The problem is that IIS is refusing to serve them because : HTTP Error 404.17 - Not Found The requested content appears to be script and will not be served by the static file handler. The folder is a subfolder of an ASP.NET application and I can't create an application just for it, neither can I change the parent application's application pool. Actually, I don't have access to the IIS configuration other than through the web.config file in the folder in question. I assume there must be a way to get a web server to serve static files, right?

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  • Network: Incoming connections work, outgoing fails

    - by anirvan
    i recently set up my own server at home to run Ubuntu 12.04 server ed. on booting up, i noticed that a message related to networking comes up, and the booting process pauses. the message read something like - waiting for network configuration and after a while - waiting another 60 seconds... on booting up, I realised that any command which requires a network connection was not working - ping, apt-get install, etc. on firing the ifup eth0 command, I get the error RTNETLINK answers: File exists. Failed to bring up eth0. I also realised, while searching the web for this problem, that this is probably one of the most common networking related issues - however, most of the questions are around setting up multiple IPs for the same machine. ifdown eth0 also fails, stating that eth0 is not configured. my /etc/network/interfaces file has a simple configuration for a static IP: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address xx.xx.xx.xx netmask xx.xx.xx.xx broadcast xx.xx.xx.xx gateway xx.xx.xx.xx dns-nameservers xx.xx.xx.xx The strangest part of this problem is that, while I can't connect to anything outside, I can ping to this particular server using the static IP configured in the interface file, and, i can even SSH into it! I'm really at ends here with this problem, and any guidance is much appreciated. Thanks!

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  • What is a good design model for my new class?

    - by user66662
    I am a beginning programmer who, after trying to manage over 2000 lines of procedural php code, now has discovered the value of OOP. I have read a few books to get me up to speed on the beginning theory, but would like some advice on practical application. So,for example, let's say there are two types of content objects - an ad and a calendar event. what my application does is scan different websites (a predefined list), and, when it finds an ad or an event, it extracts the data and saves it to a database. All of my objects will share a $title and $description. However, the Ad object will have a $price and the Event object will have $startDate. Should I have two separate classes, one for each object? Should I have a 'superclass' with the $title and $description with two other Ad and Event classes with their own properties? The latter is at least the direction I am on now. My second question about this design is how to handle the logic that extracts the data for $title, $description, $price, and $date. For each website in my predefined list, there is a specific regex that returns the desired value for each property. Currently, I have an extremely large switch statement in my constructor which determines what website I am own, sets the regex variables accordingly, and continues on. Not only that, but now I have to repeat the logic to determine what site I am on in the constructor of each class. This doesn't feel right. Should I create another class Algorithms and store the logic there for each site? Should the functions of to handle that logic be in this class? or specific to the classes whos properties they set? I want to take into account in my design two things: 1) I will add different content objects in the future that share $title and $description, but will have their own properties, so, I want to be able to easily grow these as needed. 2) I will add more websites constantly (each with their own algorithms for data extraction) so I would like to plan efficienty managing and working with these now. I thought about extending the Ad or Event class with 'websiteX' class and store its functions there. But, this didn't feel right either as now I have to manage 100s of little website specific class files. Note, I didn't know if this was the correct site or stackoverflow was the better choice. If so, let me know and I'll post there.

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  • Using a Vertex Buffer and DrawUserIndexedPrimitives?

    - by MattMcg
    Let's say I have a large but static world and only a single moving object on said world. To increase performance I wish to use a vertex and index buffer for the static part of the world. I set them up and they work fine however if I throw in another draw call to DrawUserIndexedPrimitives (to draw my one single moving object) after the call to DrawIndexedPrimitives, it will error out saying a valid vertex buffer must be set. I can only assume the DrawUserIndexedPrimitive call destroyed/replaced the vertex buffer I set. In order to get around this I must call device.SetVertexBuffer(vertexBuffer) every frame. Something tells me that isn't correct as that kind of defeats the point of a buffer? To shed some light, the large vertex buffer is the final merged mesh of many repeated cubes (think Minecraft) which I manually create to reduce the amount of vertices/indexes needed (for example two connected cubes become one cuboid, the connecting faces are cut out), and also the amount of matrix translations (as it would suck to do one per cube). The moving objects would be other items in the world which are dynamic and not fixed to the block grid, so things like the NPCs who move constantly. How do I go about handling the large static world but also allowing objects to freely move about?

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  • MediaTemple Django Bad Gateway

    - by Eeyore
    I have a site running on GS server on MediaTemple. It's Django/PostgreSQL setup. For some reason from time to time I get Bad Gateway error and I can't figure out what's causing it. What can cause this error? What else can I do to find the cause of the problem? url.access-deny = ( "~", ".inc" ) fastcgi.server = ( "/main.fcgi" => ( "main" => ( "socket" => "/var/tmp/" + appname + ".sock", # don't change this "check-local" => "disable", ) ) ) alias.url = ( "/media/" => "/home/xxx/data/python/django/django/contrib/admin/media/", "/static/" => "/home/xxx/containers/django/site/static/", ) url.rewrite-once = ( "^(/media.*)$" => "$1", "^(/static.*)$" => "$1", "^/favicon\.ico$" => "/media/favicon.ico", "^(/.*)$" => "/main.fcgi$1", ) server.error-handler-404 = "/main.fcgi"

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  • How to set up VirtualBox Bridged Network on Windows 7 Host?

    - by Tong Wang
    I have virtualbox running on a Windows 2008 server, with a guest running ubuntu 10.04. The ubuntu guest is given a static IP of 192.168.1.4, which also has openssh installed. The guest has bridged network setup, I can ping 192.168.1.4 from any machine in the LAN, the ubuntu guest can also access the LAN. However, when I try to PuTTY into the ubuntu machine, I always get "connection refused". Below are some setup details: ubuntu IP: 192.168.1.4 hosts.allow sshd : 192.168.1.38 hosts.deny ALL : ALL when I the following command, I can see that sshd is listening on port 22: lsof -i tcp:22 Any idea? EDIT: It turned out to be a wrong VirtualBox Bridged Network setup. I give the Ubuntu guest a static IP of 192.168.1.4 (assigned to eth0). Then in the Windows 7 host, in the Network and Sharing Center, there is a new connection named "VirtualBox Host-Only Network" after the bridge is setup, that connection is again given the same static IP of 192.168.1.4. Once I change the "VirtualBox Host-Only Network" to automatically obtain an IP address, it's getting a different IP address of 169.254.249.70(Tentative). And now I can SSH into 192.168.1.4 with no problem, even without touching hosts.allow and hosts.deny. I've also noticed that in the properties windows (see screenshot below) of the "VirtualBox Host-Only Network", the second checkbox, "VirtualBox Bridged Networking Driver" is unchecked. While the same checkbox of the physical NIC (that is bridged to) is checked. So my further question is: is this how VBox bridged networking supposed to be setup? Any rationale behind this? I'd appreciate if someone could provide some explaination on VBox bridged networking setup on Windows host and I'll accept it as an answer.

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  • Alternative to "inheritance versus composition?" [closed]

    - by Frank
    Possible Duplicate: Where does this concept of “favor composition over inheritance” come from? I have colleagues at work who claim that "Inheritance is an anti-pattern" and want to use composition systematically instead, except in (rare, according to them) cases where inheritance is really the best way to go. I want to suggest an alternative where we continue using inheritance, but it is strictly forbidden (enforced by code reviews) to use anything but public members of base classes in derived classes. For a case where we don't need to swap components of a class at runtime (static inheritance), would that be equivalent enough to composition? Or am I forgetting some other important aspect of composition?

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  • Tip #19 Module Private Visibility in OSGi

    - by ByronNevins
    I hate public and protected methods and classes.  It requires so much work to change them in a huge project like GlassFish.  Not to mention that you may well have to support those APIs forever.  They are highly overused in GlassFish.  In fact I'd bet that > 95% of classes are marked as public for no good reason.  It's just (bad) habit is my guess. private and default visibility (I call it package-private) is easier to maintain.  It is much much easier to change such classes and methods around.  If you have ANY public method or public class in GlassFish you'll need to grep through a tremendous amount of source code to find all callers.  But even that won't be theoretically reliable.  What if a caller is using reflection to access public methods?  You may never find such usages. If you have package private methods, it's easy.  Simply grep through all the code in that one package.  As long as that package compiles ok you're all set.  There can' be any compile errors anywhere else.  It's a waste of time to even look around or build the "outside" world.  So you may be thinking: "Aha!  I'll just make my module have one giant package with all the java files.  Then I can use the default visibility and maintenance will be much easier.  But there's a problem.  You are wasting a very nice feature of java -- organizing code into separate packages.  It also makes the code much more encapsulated.  Unfortunately to share code between the packages you have no choice but to declare public visibility. What happens in practice is that a module ends up having tons of public classes and methods that are used exclusively inside the module.  Which finally brings me to the point of this blog:  If Only There Was A Module-Private Visibility Available Well, surprise!  There is such a mechanism.  If your project is running under OSGi that is.  Like GlassFish does!  With this mechanism you can easily add another level of visibility by telling OSGi exactly which public you want to be exposed outside of the module.  You get the best of both worlds: Better encapsulation of your code so that maintenance is easier and productivity is increased. Usage of public visibility inside the module so that you can encapsulate intra-module better with packages. How I do this in GlassFish: Carefully plan out at least one package that will contain "true" publics.  This is the package that will be exported by OSGi.  I recommend just one package. Here is how to tell OSGi to use it in GlassFish -- edit osgi.bundle like so:-exportcontents:     org.glassfish.mymodule.truepublics;  version=${project.osgi.version} Now all publics declared in any other packages will be visible module-wide but not outside the module. There is one caveat: Accessing "module-private" items outside of the module is controlled at run-time, not compile-time.  The compiler has no clue that a public in a dependent module isn't really public.  it will happily compile it.  At runtime you will definitely see fireworks.  The good news is that you don't have to wait for the code path that tries to use the "module-private" items to fire.  OSGi will complain loudly when that module gets loaded.  OSGi will refuse to load it.  You will see an error like this: remote failure: Error while loading FOO: Exception while adding the new configuration : Error occurred during deployment: Exception while loading the app : org.osgi.framework.BundleException: Unresolved constraint in bundle com.oracle.glassfish.miscreant.code [115]: Unable to resolve 115.0: missing requirement [115.0] osgi.wiring.package; (osgi.wiring.package=org.glassfish.mymodule.unexported). Please see server.log for more details. That is if you accidentally change code in module B to use a public that is really a "module-private" in module A, then you will see the error immediately when you try to test whatever you were changing in module B.

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  • Whether to separate out methods or not

    - by Skippy
    I am new to java and want to learn best coding practices and understand why one method is better than another, in terms of efficiency and as the coding becomes more complicated. This is just an example, but I can take the principles from here to apply elsewhere. I have need an option to display stuff, and have put the method stuff separately from the method to ask if the user wants to display the stuff, as stuff has a lot of lines of code. For readability I have done this: public static void displayStuff () { String input = getInput ("Display stuff? Y/N \n"); if (input..equalsIgnoreCase ("Y")) { stuff (); } else if (input.equalsIgnoreCase ("N")) { //quit program } else { //throw error System.out.print("Error! Enter Y or N: \n"); } } private static String stuff () { //to lots of things here return stuff (); } Or public static void displayStuff () { String input = getInput ("Display stuff? Y/N \n"); if (input..equalsIgnoreCase ("Y")) { //to lots of things here stuff; } else if (input.equalsIgnoreCase ("N")) { //quit program } else { //throw error System.out.print("Error! Enter Y or N: \n"); } } Is it better to keep them together and why? Also, should the second method be private or public, if I am asking for data within the class? I am not sure if this is on topic for here. please advise.

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  • How cloudfront works?

    - by Dharmik Bhandari
    I'm planning to Implement CDN(Content Delivery Network) of Amazon which is known as CloudFront in ASP.NET MVC3 with c#. I've googled about it but little bit confuse about few things mentions below. Is it compulsory that we have to uploads all static resources to CDN Network first and then we can use or Is it manageable by Amazon to crawl site static resources which is predefine folder or directory of sites? Is Amazon automatic update its copies when we anything change in static resources or every time we have to upload updated resources to CDN network.

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  • Making particle bounce off a line with friction

    - by Dlaor
    So I'm making a game and I need a particle to bounce off a line. I've got this so far: public static Vector2f Reflect(this Vector2f vec, Vector2f axis) //vec is velocity { Vector2f result = vec - 2f * axis * axis.Dot(vec); return result; } Which works fine, but then I decided I wanted to be able to change the bounciness and friction of the bounce. I got bounciness down... public static Vector2f Reflect(this Vector2f vec, Vector2f axis, float bounciness) //Bounciness goes from 0 to 1, 0 being not bouncy and 1 being perfectly bouncy { var reflect = (1 + bounciness); //2f Vector2f result = vec - reflect * axis * axis.Dot(vec); return result; } But when I tried to add friction, everything went to hell and back... public static Vector2f Reflect(this Vector2f vec, Vector2f axis, float bounciness, float friction) //Does not work at all! { var reflect = (1 + bounciness); //2f Vector2f subtract = reflect * axis * axis.Dot(vec); Vector2f subtract2 = axis * axis.Dot(vec); Vector2f result = vec - subtract; result -= axis.PerpendicularLeft() * subtract2.Length() * friction; return result; } Any physics guys willing to help me out with this? (if you're not sure what I mean with the friction of a bounce see this: http://www.metanetsoftware.com/technique/diagrams/A-1_particle_collision.swf)

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  • Laptop is Switching DNS Servers

    - by Steffan Harris
    Ok sometime ago I changed my ip address to a static one because I was bored and I wanted to learn more about static ips. I am running windows xp. My laptop works find on the network that i set up a static ip address, but when i go to another network, the incorrect dns servers are being used. When I enter the option to get a dns server automatically, the internet connection works but only for a short time. After that the dns servers resets to the one i entered manually on a previous network. I did this by going to Network Connection-Right Click Local Area Connection and go to properties-Select TCP/IP - then click the Properties button. At this point i am given the option to Obtain an ip address or obtain and address automatically. My question is how do I resolve this problem of the dns server reseting to the previous one.

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  • Programming curricula

    - by davidk01
    There are a lot of schools that teach Java and C++ but whenever I see the syllabus for one of these classes it's almost always some cut and dry OO stuff with possibly some boring end of class project. With all the little gadgets and emulators for those gadgets why aren't more schools re-purposing those classes so that the students work their way up to building android or meego applications? That way students get to experience first hand what it takes to engineer/build a piece of software instead of doing finger exercises with syntax. Practically every self-taught programmer that I know started programming because they wanted to make their gadgets do things for them. They didn't learn a programming language with an abstract conception of using it on some far distant project so I don't understand why schools don't emulate this style of teaching.

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