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  • Collision detection in Java game?

    - by Chetan
    I am developing a game in which I have the problem of collision detection of moving images. The game has a spaceship and number of asteroids (obstacles). I want to detect the collision between them. How can I do this?

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  • different for lusses java

    - by Ayrton
    Hi I'm having some difficulties with the following problem: I'm making a little game where you're at a specific spot and each spot has each some possible directions. The available directions are N(ord),E(ast),S,W . I use the function getPosDirections to get the possible directions of that spot. The function returns the directions into an ArrayList e.g. for spot J3: [E,W] Now the game goes like this: 2 dices will be rolled so you get a number between 2 and 12, this number represents the number of steps you can make. What I want is an ArrayList of all the possible routes e.g.: I throw 3 and I'm currently at spot J3: [[E,N,E],[E,N,S],[E,S,E],[E,S,S],[W,N,E],[W,N,S],[W,S,E],[W,S,S]] How would obtain the last mentioned Array(list) Thanks in advance

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  • Need Java Swing equivalent of "scrollIntoView" from Browser DOM

    - by bgould
    I have a JPanel with several levels of child components, also with a JScrollPane. I'm placing a focus listener on some of the child components to add some behavior to those components, but I would also like to have that component scroll into the JPanel's viewport when focus is gained. My question is, does anyone have a general purpose function to do this, similar to the browser DOM function "scrollIntoView"? I've tried muddling through this with various inputs to JComponent.scrollRectToVisible but I guess I haven't figured out the magic word. Thanks in advance.

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  • Using Java method to display HTML code

    - by javArc
    Hey folks, ok so this is my problem, I need to display HTML code in a jsp, which wouldn't be a problem, except a requirement for this project is that we place all the code in a public class file and have seperate methods for each chunk(header, sidebar footer, etc). Now here's where i'm confused: "Your method should take the PrintWriter as a parameter to print out each line of HTML, and should have a return type of void" What does that mean? How do I pass the PrintWriter into a method? Does this make sense to anyone?

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  • Proper usage of Java Weak Reference in case of nested collections

    - by Tong Wang
    I need to define a weak reference Map, whose value is a Set. I use Google collections' MapMaker, like this: Map<Class<? extends Object>, Set<Foo>> map = new MapMaker().weakKeys().weakValues().makeMap(); So, for Set<Foo>, can I use a normal HashSet? Or, do I have to create a weak HashSet, like this: Collections.newSetFromMap(new WeakHashMap<Foo, Boolean>()); And why? Another question, the key of my map is Class objects, when will a Class object become weakly reachable? In other words, what is the lifetime of a Class object? Thanks.

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  • Java : Inner class of an interface (from google guice)

    - by bsreekanth
    Hello, I was going through the source of google guice, and found an unfamiliar piece of code. It would be great learning if someone can clarify it. I have very basic understanding of inner classes, as they keep the implementation details close to the public interface. Otherwise the inner class may pollute the namespace. Now, I see the below lines at public static final Scope SINGLETON = new Scope() { public <T> Provider<T> scope(final Key<T> key, final Provider<T> creator) { return new Provider<T>() { ......... } It assign an inner class instance to the static variable, but Scope is an interface defined as (at) public interface Scope Is it possible to instantiate the interface?? or is it a succinct syntax for an anonymous implementation of an interface?? If anyone can explain what the author is intended by multiple nested classes above (Scope and Provider), and why it make sense to implement this way, it would help me to understand. thanks.

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  • Java > SimpleDateFormat > Month + 1 Why ?

    - by Natim
    Hello, I am using SimpleDateFormat to display a Calendar like this : public String getDate() { String DATE_FORMAT = "EEEE, dd/MM/yyyy HH:mm:ss"; SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT); System.err.println(date.getTime().getMonth()); return sdf.format(date.getTime()); } The shell returns 6 and the display : mardi, 06/07/2010 12:44:52 It can't be possible ? Why ? Thanks

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  • Java serialization problem

    - by stefan89
    I have two classes X and Y, like this: class X implements Serializable { int val1; Y val2; } class Y implements Serializable { int val; } I want to transmit an object of type X from a client to server but i can't because the class X has a field of type Y. I replaced the field of type Y with a field of type X in class X and it works.

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  • Java: How to make this Serializable?

    - by Hasslarn
    I dont know that much about Serializable, but i need this class to be. How to achieve it? package helpers; public class XY implements Comparable<XY> { public int x; public int y; public XY (int x, int y) { this.x = x; this.y = y; } public int compareTo( XY other ) { String compare1 = this.x + "-" + this.y; String compare2 = other.x + "-" + other.y; return compare1.compareTo( compare2 ); } public String toString() { return this.x + "-" + this.y; } } As of now i cant send it as an object with outputstream..I´ve tried just to implement Serializable but it doesnt do the trick!

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  • Java ActionListener buttonPress() restriction

    - by Extinct23
    Is there a way to restrict this button to only being impressed once? The reason I ask is because for some reasons every time the button is pressed it disrupts the rest of my code. So in effort to save a massive amount of time debugging, it would be much easier to just somehow restrict the number of times it can be pressed. Thanks in advance. ActionListener pushButton = new buttonPress(); start.addActionListener(pushButton);

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  • Java generics conversion

    - by LittleGreenMan
    I have build a generic datacontainer and now I want to manipulate data depending on their type. However, I get an incompatable types warning. What am I doing wrong? Type _Value; public void set(Type t) throws Exception { if (_Value instanceof Integer && t instanceof Integer) { _Value = (((Integer) t - _MinValue + getRange()) % getRange()) + _MinValue; } else if (_Value instanceof Boolean && t instanceof Boolean) { _Value = t; } else throw new Exception("Invalid type"); }

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  • Java Web Server with Jetty - TCP Connections Taking Long

    - by daysleeper
    I have an application with fairly high traffic (20K req/min) running on the JVM with a Jetty servlet container on Ubuntu. Below is my Jetty configuration: 10 20 2000 2 When I analyze the network traffic, I realize that sometimes it is taking long to establish TCP connections on the port that Jetty is running. The long connections are varying between 3.0s and 9.0s. The port is configured to accept MAX number of TCP connections. Do you know what might be causing the delay in accepting connections? Thanks

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  • Trimming byte array when converting byte array to string in Java/Scala

    - by prosseek
    Using ByteBuffer, I can convert a string into byte array: val x = ByteBuffer.allocate(10).put("Hello".getBytes()).array() > Array[Byte] = Array(104, 101, 108, 108, 111, 0, 0, 0, 0, 0) When converting the byte array into string, I can use new String(x). However, the string becomes hello?????, and I need to trim down the byte array before converting it into string. How can I do that? I use this code to trim down the zeros, but I wonder if there is simpler way. def byteArrayToString(x: Array[Byte]) = { val loc = x.indexOf(0) if (-1 == loc) new String(x) else if (0 == loc) "" else new String(x.slice(0,loc)) }

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  • java threads don't see shared boolean changes

    - by andymur
    Here the code class Aux implements Runnable { private Boolean isOn = false; private String statusMessage; private final Object lock; public Aux(String message, Object lock) { this.lock = lock; this.statusMessage = message; } @Override public void run() { for (;;) { synchronized (lock) { if (isOn && "left".equals(this.statusMessage)) { isOn = false; System.out.println(statusMessage); } else if (!isOn && "right".equals(this.statusMessage)) { isOn = true; System.out.println(statusMessage); } if ("left".equals(this.statusMessage)) { System.out.println("left " + isOn); } } } } } public class Question { public static void main(String [] args) { Object lock = new Object(); new Thread(new Aux("left", lock)).start(); new Thread(new Aux("right", lock)).start(); } } In this code I expect to see: left, right, left right and so on, but when Thread with "left" message changes isOn to false, Thread with "right" message don't see it and I get ("right true" and "left false" console messages), left thread don't get isOn in true, but right Thread can't change it cause it always see old isOn value (true). When i add volatile modifier to isOn nothing changes, but if I change isOn to some class with boolean field and change this field then threads are see changes and it works fine Thanks in advance.

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  • What is a good "Error Checking" Pattern (Java)?

    - by Jack
    I'll explain what I mean by input error checking. Say you have a function doSomething(x). If the function completes successfully doSomething does something and returns nothing. However, if there are errors I'd like to be notified. That is what I mean by error checking. I'm looking for, in general, the best way to check for errors. I've thought of the following solutions, each with a potential problem. Flag error checking. If doSomething(x) completes successfully return null. Otherwise, it returns a boolean or an error string. Problem: Side effects. Throwing an exception. Throw an exception if doSomething(x) encounters an error. Problem: If you are performing error checking for parameters only, throwing an IllegalArgumentExceptionseems inappropriate. Validating input prior to function call. If the error checking is only meant for the parameters of the function, then you can call a validator function before calling the doSomething(x) function. Problem: What if a client of the class forgets to call the validator function before calling doSomething(x)? I often encounter this problem and any help or a point in the right direction would be much appreciated.

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  • Java Disabled JLabel Reports Mouse Clicked

    - by ikurtz
    colLabels[i].addMouseListener(new MyAdapter()); private class MyAdapter extends MouseAdapter { @Override public void mouseClicked(MouseEvent event) { ColJLabel colJLabel = (ColJLabel)event.getComponent(); System.out.println(colJLabel.ColID); setColumnHeader(false); } } colLabels[i].setEnabled(flag); The situation is this: Mouse clicks are trapped correctly but when i have the JLabel (ColJLabel) control disabled it still reports mouse clicks. How can I make so that mouse clicks are only reported when the control is enabled? Thanks.

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  • Java - What's the most efficient way of removing a set of elements from an Array[]

    - by fraido
    I've something like this Object[] myObjects = ...(initialized in some way)... int[] elemToRemove = new int[]{3,4,6,8,...} What's the most efficient way of removing the elements of index position 3,4,6,8... from myObjects ? I'd like to implement an efficient Utility method with a signature like public Object[] removeElements(Object[] object, int[] elementsToRemove) {...} The Object[] that is returned should be a new Object of size myObjects.length - elemToRemove.length

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  • java.lang.classcastExcption

    - by Tara Singh
    Hi, I have an array list of objects in my application. private static ArrayList<Player> userList=new ArrayList<Player>(); In my application, I am converting this list to byte array and then sending it to other clients. At client When I am trying to cast it back to the ArrayList, its giving me casting error. I am doing this in client side after receiving this list as byte array: ArrayList<Player> pl = (ArrayList<Player>) toObject(receivedByteArray); where toObject is my function to convert the byte array to object; Any Suggestions please !!! Thanks.

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