Lecture/객체지향프로그래밍및실습/Timer를 이용한 Random Balls

import acm.program.*;
import acm.util.*;
import acm.graphics.*;
 
import java.awt.event.*;
import java.util.*;
 
public class RandomBallsTimer extends GraphicsProgram {
 
    @Override
    public void init() {
        addMouseListeners();
        addMouseMotionListener(this);
        addKeyListeners();
    }
 
    @Override
    public void run() {
        terminated = false;
 
        ActionListener listener = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                moveOneStep();
            }
        };
 
        SwingTimer timer = new SwingTimer(TIMER_RATE, listener);
        timer.start();
    }
 
    public void moveOneStep() {
        if (clear) {
            removeAll();
            clear = false;
        }
 
        if (reserved2Remove != null) {
            remove(reserved2Remove);
            reserved2Remove = null;
        }
 
        if (!paused)
            moveObjects();
    }
 
    @Override
    public void keyPressed(KeyEvent e) {
        switch(e.getKeyCode()) {
        case KeyEvent.VK_Q :
                    shutdown();
                    break;
        case KeyEvent.VK_P :
                    paused = !paused;
                    break;
        case KeyEvent.VK_C :
                    clear = true;
                    break;
        case KeyEvent.VK_N :
                    createRandomBall();
                    break;
        }
    }
 
    @Override
    public void mousePressed(MouseEvent e) {
        createRandomBall();
    }
 
    @Override
    public void mouseMoved(MouseEvent e) {
        if (reserved2Remove == null)
            reserved2Remove = getElementAt(e.getX(), e.getY());
    }
 
    private void createRandomBall() {
        double w = random.nextDouble(MIN_SIZE, MAX_SIZE);
        GDimension vec = new GDimension(random.nextDouble(MIN_VELOCITY, MAX_VELOCITY),
                                        random.nextDouble(MIN_VELOCITY, MAX_VELOCITY));
        double dx = random.nextDouble(w, getWidth() - w);
        double dy = random.nextDouble(w, getHeight() - w);
 
        GMovingBall ball = new GMovingBall(w, vec, dx, dy);
        ball.setColor(random.nextColor());
        add(ball);
    }
 
    public void moveObjects() {
        Iterator<GObject> it = this.iterator();
        while (it.hasNext()) {
            GObject gobj = it.next();
            if (gobj instanceof GMovingBall) {
                GMovingBall ball = (GMovingBall)gobj;
                double r = ball.getWidth() / 2;
                boolean directionIsChanged = false;
 
                double vecX = ball.getVectorX();
                double nextX = ball.getX() + vecX;
                double wallX = getWidth() - r;
                if (nextX >= wallX || nextX <= r) {
                    if (nextX >= wallX) {
                        nextX = wallX - (nextX - wallX);
                    } else {
                        nextX = (nextX < 0) ? r - nextX : r + (r - nextX);
                    }
                    vecX = -vecX;
                    directionIsChanged = true;
                }
 
                double vecY = ball.getVectorY();
                double nextY = ball.getY() + vecY;
                double wallY = getHeight() - r;
                if (nextY > wallY || nextY < r) {
                    if (nextY > wallY) {
                        nextY = wallY - (nextY - wallY);
                    } else {
                        nextY = (nextY < 0) ? r - nextY : r + (r - nextY);
                    }
                    vecY = -vecY;
                    directionIsChanged = true;
                }
 
                if (directionIsChanged) {
                    ball.setVector(vecX, vecY);
                }
                ball.setLocation(nextX, nextY);
            }
        }
    }
 
    private void shutdown() {
        terminated = true;
        removeAll();
    }
 
    /* Private static final constants */
    private static final long MIN_SIZE = 1;
    private static final long MAX_SIZE = 50;
    private static final long MIN_VELOCITY = -10;
    private static final long MAX_VELOCITY = 10;
    private static final int TIMER_RATE = 20;
 
    //private ArrayList arr = new ArrayList();
    private boolean terminated = false;
    private boolean paused = false;
    private boolean clear = false;
    private GObject reserved2Remove = null;
    private RandomGenerator random = RandomGenerator.getInstance();
 
    public static final long serialVersionUID = 1;
}