Errors while trying to build an asteroid game in java

Question

I've been trying to create the first part of an asteroid game in java that simply displays 20 asteroids moving around in a field. When ever I go to start it I get these errors:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at blobzx.SandBox$1.actionPerformed(SandBox.java:82)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6535)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6300)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4891)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4713)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

I've looked through other articles here but cannot seem to find a solution for this scenario. Here is the code I have written:

    package AsteroidField;

import blobzx.*;
import java.awt.Point;
import java.util.Random;

public class AsteroidField implements BlobGUI{

    Random random;

    SandBox sand = new SandBox();

   public static void main( String[] args){


        new AsteroidField();
    }

    public AsteroidField(){

        this.random = new Random();

    }

    public void init(){

        sand.setSandBoxMode(SandBoxMode.FLOW);
        sand.setFrameRate(15);
        sand.init(this);

    }

    public void generate(){

        for(int i=0; i<20; i++){

           int idx = random.nextInt(6)-3;
           int idy = random.nextInt(6)-3;
           double rot = (random.nextInt(2)-1)*.1;

            PolyBlob a = new Asteroid(idx, idy, rot);
            sand.addBlob(a);
        }

        SandBox.simulate(sand);

    }
}

    package AsteroidField;

import blobzx.*;
import java.util.Random;
import java.awt.Point;

public class Asteroid extends PolyBlob {

    private Random random = new Random();

    public Asteroid(int idx, int jdx, double rot ){


        super( -100, -100, rot );


        setDelta(idx, jdx);

        int sides = random.nextInt(4)+5;
        int pix = random.nextInt(20)+10;

        int[] x = new int [-100];
        int[] y = new int [-100];
        double[] angle = new double [1];

        for(int i=0; i<sides; i++){

            double region = ((Math.PI*2)/sides);
            angle[i] = (i*region)+(Math.random()*region);

        }

        for(int j=0; j<sides; j++){

            int distance = random.nextInt(10)+5;
            Point point = BlobUtils.rotatePoint(distance, angle[j]);

            x[j] = point.x;
            y[j] = point.y;

        }

        setPolygon(x, y);

    }
}

Any help on this issue would be greatly appreciated.

The stack trace is pretty clear that your error is occurring in your `SandBox` class, so you should probably include that class's code (or at least all of the ActionListeners it creates) in your question. — VGR, Feb 25 '16 at 23:59
The stacktrace shows you where the exception occurs, so check this/these code line(s)? — Tom, Feb 25 '16 at 23:59

score 0 · Answer 1 · edited Feb 26 '16 at 00:05

The one thing I saw that struck out at me right away were the lines:

int[] x = new int [-100];
int[] y = new int [-100];

Error I got after compiling just these phrases embeded in a java Program.

Exception in thread "main" java.lang.NegativeArraySizeException
    at HelloWorld.main(HelloWorld.java:5)

I assume that other basic syntax errors probably exist so you should check your basic syntax.

Errors while trying to build an asteroid game in java

1 Answers1