BallCollisionProgram

BallCollisionProgram.java

import acm.graphics.*;
import acm.util.*;
import java.awt.event.*;
import java.util.*;
 
public class BallCollisionProgram extends RandomBalls {
 
    @Override
    public void run() {
        ActionListener listener = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                moveOneStep();
            }
        };
        SwingTimer timer = new SwingTimer(TIMER_RATE, listener);
        timer.start();
    }
 
    @Override
    public void mouseMoved(MouseEvent e) {
        // nothing
    }
 
    @Override
    public void moveObjects() {
        super.moveObjects();
 
        ArrayList<GObject> removedObjs = new ArrayList<GObject>();
 
        Iterator<GObject> it = iterator();
        while (it.hasNext()) {
            Iterator<GObject> it2 = iterator();
            GBall gobj = (GBall)it.next();
 
            while (it2.hasNext()) {
                GBall target = (GBall)it2.next();
                if (target == gobj)
                    continue;
                // collision check
                double distance = GMath.distance(gobj.getX(), gobj.getY(), 
                                                 target.getX(), target.getY());
                if (distance - (gobj.getRadius() + target.getRadius()) <= 0.00001) {
                    // collision
                    if (gobj.getRadius() < target.getRadius()) {
                        target.setRadius(target.getRadius() - gobj.getRadius());
                        removedObjs.add(gobj);
                    } else if (gobj.getRadius() > target.getRadius()) {
                        gobj.setRadius(gobj.getRadius() - target.getRadius());
                        removedObjs.add(target);
                    } else {
                        removedObjs.add(gobj);
                        removedObjs.add(target);
                    }
                    System.out.println("BOOM");
                }
            }
        }
        for (int i = 0; i < removedObjs.size(); i++) {
            remove(removedObjs.get(i));
        }
    }	
 
    public static void main(String[] arg) {
        new BallCollisionProgram().start();
    }
 
    private static final int TIMER_RATE = 20;
 
    public static final long serialVersionUID = 1;
}

GBall.java

/*
 * File: GBall.java
 * ----------------
 * This file defines a GObject class that represents a ball.
 */
import acm.graphics.*;
 
/**
 * This class defines a GCompound subclass that represents a ball
 * whose reference point is the center rather than the upper
 * left corner.
 */
public class GBall extends GCompound {
 
/** Creates a new ball with radius r centered at the origin */
    public GBall(double r) {
        radius = r;
        ball = new GOval(2 * radius, 2 * radius);
        ball.setFilled(true);
        add(ball, -radius, -radius);
 
        markAsComplete();
    }
 
    /** Creates a new ball with radius r centered at (x, y) */
    public GBall(double r, double x, double y) {
        this(r);
        setLocation(x, y);
    }
 
    public void setRadius(double r) {
        ball.setSize(r * 2, r * 2);
    }
 
    public double getRadius() {
        return radius;
    }
 
    /*
    public void setSize(double r) {
        ball.setSize(r, r);
    }
 
    public double getWidth() {
        return ball.getWidth();
    }
 
    public double getHeight() {
        return ball.getHeight();
    }
    */
 
    private GOval ball;
    private double radius;
}