Java核心技术 卷II 线程

ackage test;

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;

/**
Shows an aninated bouncing ball.
*/
public class Bounce{
public static void main(String[] args){
JFrame frame = new BounceFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
/*
A ball that moves and bounces off edges of a rectangle.
*/
class Ball{
/*
Moves the ball to the next position, reversing directon
if it hits one of the edges.
*/
private static final int XSIZE = 15;
private static final int YSIZE = 15;
private double x = 0;
private double y = 0;
private double dx = 1;
private double dy = 1;
public void move(Rectangle2D bounds){
x +=dx;
y +=dy;
if(x<bounds.getMinX()){
x = bounds.getMinX();
dx = -dx;
}
if(x + XSIZE >= bounds.getMaxX()){
x = bounds.getMaxX() - XSIZE;
dx = -dx;
}
if(y<bounds.getMinY()){
y = bounds.getMinY();
dy = -dy;
}
if(y + YSIZE >= bounds.getMaxY()){
y = bounds.getMaxY() - YSIZE;
dy = -dy;
}
}
/*
*Gets the shape of the ball at its current position.
*/
public Ellipse2D getShape(){
return new Ellipse2D.Double(x,y,XSIZE,YSIZE);
}
}

/*
* The frame with panel and buttons.
*/
class BounceFrame extends JFrame{
/*
* Construct the frame with the panel for showing the bouncing ball and
* start and close buttons.
*/
private BallPanel panel;
public static final int DEFAULT_WIDTH = 450;
public static final int DEFAULT_HEIGHT = 500;
public static final int STEPS = 1000;
public static final int DELAY = 3;

public BounceFrame(){
setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
setTitle("Bounce");

panel = new BallPanel();
add(panel, BorderLayout.CENTER);
JPanel buttonPanel = new JPanel();
addButton(buttonPanel,"start",
new ActionListener(){
public void actionPerformed(ActionEvent event){
addBall();
}
});
addButton(buttonPanel,"Close",
new ActionListener(){
public void actionPerformed(ActionEvent event){
System.exit(0);
}
});       
add(buttonPanel,BorderLayout.SOUTH);
}
/*
* adds a button to a container.
* @param c the container
* @param title the button title
* @param listener the action listener for the button
*/
public void addButton(Container c, String title, ActionListener listener){
JButton button = new JButton(title);
c.add(button);
button.addActionListener(listener);
}
/*
* add a ball to the panel and makes it bounce 1k times
*/
public void addBall(){
Ball ball = new Ball();
panel.add(ball);

Runnable r = new BallRunnable(ball,panel);
Thread t = new Thread(r);
t.start();
}   
}
/*
* the panel that draws the balls.
*/
class BallPanel extends JPanel{
private ArrayList<Ball> balls = new ArrayList<Ball>();
/*
* add a ball to the panel.
* @param b the ball to add
*/   
public void add(Ball b){
balls.add(b);
}
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.ORANGE);
for (Ball b:balls) {   
g2.fill(b.getShape());
}
}
}

/*
* A runnable that animate a bouncing ball.
*/
class BallRunnable implements Runnable{
private Ball ball;
private Component component;
public static final int STEPS = 10000;
public static final int DELAY = 3;

public BallRunnable(Ball aball, Component acomponent) {
// TODO Auto-generated constructor stub
ball = aball;
component = acomponent;
}

@Override
public void run() {
try {
for (int i = 0; i <= STEPS; i++) {
ball.move(component.getBounds());
component.repaint();//BallPanel
Thread.sleep(DELAY);
}
} catch ( InterruptedException e) {
// TODO: handle exception
}

}

}
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