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  • java dynamic memory allocation?

    - by JavaUser
    Hi, Why an object initialization using " new " keyword is called as dynamic memory allocation since compile time itself we know the memory needed for that object . Also please explain what happen when u do ClassA object = new ClassA(); in heap and stack . Thx

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  • Sum up values in an array list in java

    - by user1449997
    Hello to all tired and frustrated programmers, There is a problem I can't solve: In my array list there are Object arrays with the length of three and always on the last cell of the array there is a double. I need a loop which goes through the array list and sums up all doubles. (I need also some other thing from the arrays so a general idea how to loop through an array list would be perfect :-)) Any ideas? Thanks for your help, Greetings Demian

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  • Java multi Generic collection parameters complie error

    - by Geln Yang
    Hi, So strange!Please have a look the code first: public class A { } public class B extends A { } public class C extends A { } public class TestMain { public <T extends A> void test(T a, T b) { } public <T extends A> void test(List<T> a, List<T> b) { } public static void main(String[] args) { new TestMain().test(new B(), new C()); new TestMain().test(new ArrayList<B>(), new ArrayList<C>()); } } The statement "new TestMain().test(new ArrayList(), new ArrayList())" get a "Bound mismatch" compile error, while "new TestMain().test(new B(), new C())" is compiled ok. Bound mismatch: The generic method test(T, T) of type TestMain is not applicable for the arguments (ArrayList, ArrayList). The inferred type ArrayList is not a valid substitute for the bounded parameter It seems the type of the second generic List parameter is limited by the Type of the first.Is it a feature or a bug of the compile program? ps, jdk:1.6,IDE:Eclipse 3.5.1

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  • Java: how to name boolean properties

    - by NoozNooz42
    I just had a little surprise in a Webapp, where I'm using EL in .jsp pages. I added a boolean property and scratched my head because I had named a boolean "isDynamic", so I could write this: <c:if test="${page.isDynamic}"> ... </c:if> Which I find easier to read than: <c:if test="${page.dynamic}"> ... </c:if> However the .jsp failed to compile, with the error: javax.el.PropertyNotFoundException: Property 'isDynamic' not found on type com... I turns out my IDE (and it took me some time to notice it), when generating the getter, had generated a method called: isDynamic() instead of: getIsDynamic() Once I manually replaced isDynamic() by getIsDynamic() everything was working fine. So I've got really two questions here: is it bad to start a boolean property's name with "is"? wether it is bad or not, didn't IntelliJ made a mistake here by auto-generating a method named isDynamic instead of getIsDynamic?

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  • Import text file crunching library for Java/Groovy ?

    - by devdude
    In a lot of real life implementations of applications we face the requirement to import some kind of (text) files. Usually we would implement some (hardcoded?) logic to validate the file (eg. proper header, proper number of delimiters, proper date/time value,etc.). Eventually also need to check for the existence of related data in a table (eg. value of field 1 in text file must have an entry in some basic data table). While XML solves this (to some extend) with XSD and DTD, we end up hacking this again and again for proprietary text file formats. Is there any library or framework that allows the creation of templates similar to the xsd approach ? This would make it way more flexible to react on file format changes or implement new formats. Thanks for any hints Sven

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  • Java How to get exact tile location in random tile engine

    - by SYNYST3R1
    I am using the slick2d library. I want to know how to get the exact tile location so when I click on a tile it only changes that tile and not every tile on the screen. My tile generation class public Image[] tiles = new Image[3]; public int width, height; public int[][] index; public Image grass, dirt, selection; boolean selected; int mouseX, mouseY; public void init() throws SlickException { grass = new Image("assets/tiles/grass.png"); dirt = new Image("assets/tiles/dirt.png"); selection = new Image("assets/tiles/selection.png"); tiles[0] = grass; tiles[1] = dirt; width = 50; height = 50; index = new int[width][height]; Random rand = new Random(); for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { index[x][y] = rand.nextInt(2); } } } public void update(GameContainer gc) { Input input = gc.getInput(); mouseX = input.getMouseX(); mouseY = input.getMouseY(); if(input.isMouseButtonDown(Input.MOUSE_LEFT_BUTTON)) { selected = true; } else{ selected = false; } } public void render() { for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { tiles[index[x][y]].draw(x * 64, y *64); if(IsMouseInsideTile(x, y)) selection.draw(x * 64, y * 64); } } } public boolean IsMouseInsideTile(int x, int y) { return (mouseX >= x * 64 && mouseX <= (x + 1) * 64 && mouseY >= y * 64 && mouseY <= (y + 1) * 64); } I have tried a couple different ways to change the tile I am clicking on, but I don't understand how to do it.

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  • Problem loading java properties

    - by markovuksanovic
    I am trying to load properties from a file (test.properties) The code I use is as follows: URL url = getClass().getResource("../resources/test.properties"); properties.load(url.openStream()); But when executing the second line I get a NPE. (null pointer exception) I'm not sure what's wrong here... I have checked that the file exists at the location where URL points to... Any help is appreciated....

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  • java - powermock whenNew doesnt seem to work, calls the actual constructor

    - by user1331243
    I have two final classes that are used in my unit test. I am trying to use whenNew on the constructor of a final class, but I see that it calls the actual constructor. The code is @PrepareForTest({A.class, B.class, Provider.class}) @Test public void testGetStatus() throws Exception { B b = mock(B.class); when(b.getStatus()).thenReturn(1); whenNew(B.class).withArguments(anyString()).thenReturn(b); Provider p = new Provider(); int val = p.getStatus(); assertTrue((val == 1)); } public class Provider { public int getStatus() { B b = new B("test"); return b.getStatus(); } } public final class A { private void init() { // ...do soemthing } private static A a; private A() { } public static A getInstance() { if (a == null) { a = new A(); a.init(); } return a; } } public final class B { public B() { } public B(String s) { this(A.getInstance(), s); } public B(A a, String s) { } public int getStatus() { return 0; } } On debug, I find that its the actual class B instance created and not the mock instance that is returned for new usage and assertion fails. Any pointers on how to get this working. Thanks

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  • Second level cache for java web app and its alternatives

    - by EugeneP
    Between the transitions of the web app I use a Session object to save my objects in. I've heard there's a program called memcached but there's no compiled version of it on the site, besides some people think there are real disadvantages of it. Now I wanna ask you. What are alternatives, pros and cons of different approaches? Is memcached painpul for sysadmins to install? Is it difficult to embed it to the existing infrastructure from the perspective of a sysadmin? What about using a database to hold temporary data between web app transitions? Is it a normal practice?

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  • String replaceAll method (Java)

    - by Mr CooL
    I have following problem, Code: String a="Yeahh, I have no a idea what's happening now!"; System.out.println(a); a=a.replaceAll("a", ""); System.out.println(a); Before removing 'a', result: Yeahh, I have no a idea what's happening now! Actual Result: After removing 'a', result: Yehh, I hve no ide wht's hppening now! Desired Result: Yeahh, I have no idea what's happening now! Anyone can gimme some advices to achieve my desired result?

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  • How to insert date in sqlite through java.

    - by dimitar
    Hello guys, I want to make a database that will hold a date in it(SQLite). Now first to ask is what is the right syntax to declare a date column. The second i want to know is how to insert date in it after that. And the third thing i want to know is how to select dates between, for example to select all rows which contain date between 01/05/2010 and 05/06/2010. Thank you

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  • Java Concurrency : Volatile vs final in "cascaded" variables?

    - by Tom
    Hello Experts, is final Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); the same as volatile Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); in case the inner Map is accessed by different Threads? or is even something like this required: volatile Map<Integer,Map<String,Integer>> status = new ConcurrentHashMap<Integer, Map<String,Integer>>(); volatile Map<Integer,Map<String,Integer>> statusInner = new ConcurrentHashMap<Integer, Map<String,Integer>>(); status.put(key,statusInner); In case the it is NOT a "cascaded" map, final and volatile have in the end the same effect of making shure that all threads see always the correct contents of the Map... But what happens if the Map iteself contains a map, as in the example... How do I make shure that the inner Map is correctly "Memory barriered"? Tanks! Tom

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  • Java Reflection Utility

    - by DD
    Is there a utility to get a property which isnt prefixed by get from an object using reflection similar to BeanUtils? e.g. if I specify "hashcode" and I want to get the object.hashcode() value. Thanks.

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  • How to replace characters in a java String?

    - by ManBugra
    I like to replace a certain set of characters of a string with a corresponding replacement character in an efficent way. For example: String sourceCharacters = "šdccŠÐCCžŽ"; String targetCharacters = "sdccSDCCzZ"; String result = replaceChars("Gracišce", sourceCharacters , targetCharacters ); Assert.equals(result,"Gracisce") == true; Is there are more efficient way than to use the replaceAll method of the String class? My first idea was: final String s = "Gracišce"; String sourceCharacters = "šdccŠÐCCžŽ"; String targetCharacters = "sdccSDCCzZ"; // preparation final char[] sourceString = s.toCharArray(); final char result[] = new char[sourceString.length]; final char[] targetCharactersArray = targetCharacters.toCharArray(); // main work for(int i=0,l=sourceString.length;i<l;++i) { final int pos = sourceCharacters.indexOf(sourceString[i]); result[i] = pos!=-1 ? targetCharactersArray[pos] : sourceString[i]; } // result String resultString = new String(result); Any ideas? Btw, the UTF-8 characters are causing the trouble, with US_ASCII it works fine.

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  • Java KeyListener in separate class

    - by Chris
    So I have my main class here, where basically creates a new jframe and adds a world object to it. The world object is basically where all drawing and keylistening would take place... public class Blobs extends JFrame{ public Blobs() { super("Blobs :) - By Chris Tanaka"); setVisible(true); setResizable(false); setSize(1000, 1000); setIgnoreRepaint(true); setDefaultCloseOperation(EXIT_ON_CLOSE); add(new World()); } public static void main(String[] args) { new Blobs(); } } How exactly would you get key input from the world class? (So far I have my world class extending a jpanel and implementing a keylistener. In the constructor i addKeyListener(this). I also have these methods since they are auto implemented: public void keyPressed(KeyEvent e) { if (e.getKeyCode() == KeyEvent.VK_W) System.out.println("Hi"); } public void keyReleased(KeyEvent e) {} public void keyTyped(KeyEvent e) {} However this does not seem to work?

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  • FTPing a file to Mainframe using Java, Apache Common Net

    - by SKR
    I'm am trying to upload a file into mainframe server using FTP. My code is below FTPClient client = new FTPClient(); InputStream in = null; FileInputStream fis = null; try{ client.connect("10.10.23.23"); client.login("user1", "pass123"); client.setFileType(FTPClient.BINARY_FILE_TYPE); int reply ; reply = client.getReplyCode(); System.out.println("Reply Code:"+reply); if(FTPReply.isPositiveCompletion(reply)){ System.out.println("Positive reply"); String filename ="D:\\FILE.txt"; in = new FileInputStream(filename); client.storeFile("FILE.TXT", in); client.logout(); fis.close(); }else{ System.out.println("Negative reply"); } }catch(final Throwable t){ t.printStackTrace(); } The code gets struck in client.storeFile("FILE.TXT", in); I am unable to debug. Please suggest ways / solutions.

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  • java applet - javascript communication

    - by udhaya
    Applet Communication: write a small applet and embed it in html-file with following functionality. 1. change applet bg color by receiving a javascript command with the color parameter. 2. show dynamic mouse position in applet-window and display position in html-site. use live-connect between applet and browser communication.

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  • Create A Java Variable (String) of a specific size (MB's)

    - by Bernie Perez
    I am trying to benchmark some code. I am sending a String msg over sockets. I want to send 100KB, 2MB, and 10MB String variables. Is there an easy way to create a variable of these sizes? Currently I am doing this. private static String createDataSize(int msgSize) { String data = "a"; while(data.length() < (msgSize*1024)-6) { data += "a"; } return data; } But this takes a very long time. Is there a better way?

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  • Java: Line appears when using AffineTransform to scale image

    - by Malakim
    Hi, I'm having a problem with image scaling. When I use the following code to scale an image it ends up with a line either at the bottom or on the right side of the image. double scale = 1; if (scaleHeight >= scaleWidth) { scale = scaleWidth; } else { scale = scaleHeight; } AffineTransform af = new AffineTransform(); af.scale(scale, scale); AffineTransformOp operation = new AffineTransformOp(af, AffineTransformOp.TYPE_NEAREST_NEIGHBOR); BufferedImage bufferedThumb = operation.filter(img, null); The original image is here: http://tinyurl.com/yzv6r7h The scaled image: http://tinyurl.com/yk6e8ga Does anyone know why the line appears? Thanks!

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