Java课程设计，多色弹弹球

package cn.hncu.MyThread2;


import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;


import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSpinner;
import javax.swing.Timer;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;


public class BallsJFrame2 extends JFrame implements ChangeListener,ActionListener{

//这些变量需要做事件监听，因此不能放在构造方法里面
private JSpinner spinner;
private RollBalls ball;
private JButton btn1,btn2;

public BallsJFrame2(){
super("Rolling balls");
this.setBounds(400, 200, 700, 600);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);//设置关闭窗口的功能
this.setResizable(false);//设置窗口不能拉大拉小，true为能够拉伸
Color colors[]={Color.black,Color.blue,Color.cyan,Color.DARK_GRAY,Color.green,
Color.red,Color.magenta,Color.orange,Color.pink,Color.yellow};//为每一个球设置颜色

//建立球的对象，同时会将整个画布添加进去
ball=new RollBalls(100, colors);
this.getContentPane().add(ball);

JPanel panel=new JPanel();
this.getContentPane().add(panel,"South");
panel.add(new JLabel("delay"));
spinner=new JSpinner();
spinner.setValue(100);
panel.add(spinner);
spinner.addChangeListener(this);

btn1=new JButton("start");
btn1.setEnabled(false);
btn1.addActionListener(this);
panel.add(btn1);

btn2=new JButton("stop");
btn2.addActionListener(this);
panel.add(btn2);

this.setVisible(true);
}

public static void main(String[] args) {
new BallsJFrame2();
}


@Override//延迟状态改变时监听
public void stateChanged(ChangeEvent e) {
int value=Integer.parseInt(""+spinner.getValue());
ball.setDelay(value);
}


@Override
public void actionPerformed(ActionEvent e) {
if (e.getSource()==btn1) {
btn1.setEnabled(false);
btn2.setEnabled(true);
ball.setStart();
}
if (e.getSource()==btn2) {
btn1.setEnabled(true);
btn2.setEnabled(false);
ball.setStop();
}
}
}


class RollBalls extends Canvas implements ActionListener{
private Balls balls[];
private int delay;
private Timer timer;
public RollBalls(int delay,Color colors[]){
this.delay=delay;
balls=new Balls[colors.length];

//将每一个球对象的位置和大小确定
for (int i = 0,x=40; i < balls.length; i++,x+=20) {
balls[i]=new Balls(x, x, colors[i]);
}
timer=new Timer(delay, this);
timer.start();//启动线程
}

public void setDelay(int delay){
timer.setDelay(delay);
}

public void setStop(){
timer.stop();
}

public void setStart(){
timer.restart();
}

@Override
public void paint(Graphics g) {
for (int i = 0; i < balls.length; i++) {
g.setColor(balls[i].color);

balls[i].x=balls[i].left? balls[i].x-10:balls[i].x+10;
if (balls[i].x<=0||balls[i].x>=this.getWidth()-20) {
balls[i].left=!balls[i].left;
}

balls[i].y=balls[i].up? balls[i].y-10:balls[i].y+10;
if (balls[i].y<=0||balls[i].y>=this.getHeight()-20) {
balls[i].up=!balls[i].up;
}

g.fillOval(balls[i].x, balls[i].y, 20, 20);
}
}

class Balls{
private int x,y;
private Color color;
private boolean left,up;

public Balls(int x,int y,Color color){
this.x=x;
this.y=y;
this.color=color;
left=up=false;
}
}




@Override
public void actionPerformed(ActionEvent e) {
repaint();
}
}