import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;

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

public class ballsJFrame extends JFrame implements ChangeListener{

    private JSpinner spinner;//微調按鈕
 

    private ballsCanvas canvas;//用畫布畫球
    public ballsJFrame() {
        super("彈彈球");
        setBounds(300, 200, 400, 300);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        Color colors[]={Color.red ,Color.yellow ,Color.BLUE,Color.green,Color.gray};//小球顏色及個數

        canvas=new ballsCanvas(colors, 100
 
);//new一個畫布
        getContentPane().add(canvas);

        JPanel panel=new JPanel();
        getContentPane().add(panel,BorderLayout.SOUTH);//getContentPane().add(panel,"SOUTH");
        panel.add(new JLabel("dalay"));
        spinner =new JSpinner();//new一個微調按鈕
        spinner.setValue(100);//設定初始值new ballsCanvas(colors, 100);
        panel.add(spinner);
        spinner.addChangeListener(this);//監聽裡面的數值發生變化

        setVisible(true);
    }
    public static void main(String[] args) {

        new ballsJFrame();
    }

    public void stateChanged(ChangeEvent e) {

        int delay=Integer.parseInt(""+spinner.getValue());//獲取微調按鈕文本里的值
        canvas.setDelay(delay);//對timer設定數值
    }

}
class ballsCanvas extends Canvas implements ActionListener, FocusListener{

    private ball balls[];//球
    private Timer timer;//定時器
    class ball{//內部類，，底下畫球時就可以直接呼叫座標，不用getX（）函式
        private int x,y;
        private Color color;
        boolean up,left;//初始值是false
        public ball(int x, int y, Color color) {
            this.x = x;
            this.y = y;
            this.color = color;
        }

    }

    public ballsCanvas(Color[] colors,int delay) {
        this.balls = new ball[colors.length];
        for(int i=0,x=40;i<colors.length;i++,x+=40){
            balls[i]=new ball(x,x,colors[i]);
        }

        this.addFocusListener(this);//監聽焦點
        timer=new Timer(delay,this);//用法和btn.addActionLis一樣
        timer.start();//定時器本身是一個執行緒物件，必須要啟動才會生效
    }
    public void setDelay(int delay){//在ballsJFrame 類中的方法進行設定數值
        timer.setDelay(delay);
    }
    public void paint(Graphics g) {//畫筆
        for(int i=0;i<balls.length;i++){
            g.setColor(balls[i].color);//用當前顏色畫球
            //方法1：
            balls[i].x=balls[i].left? balls[i].x-5 : balls[i].x+5 ;
            //遇到邊界就改變方向
            if(balls[i].x<=0 || balls[i].x+20>=this.getWidth()){//balls[i].x+20和balls[i].y+20因為球的座標是 **球外接正方形左上方的那一點**，所以判斷球碰到下面和右邊的邊界時要加上求的直徑g.fillOval(balls[i].x, balls[i].y, 20, 20);
                balls[i].left=!balls[i].left;
            }
            balls[i].y=balls[i].up? balls[i].y-5 : balls[i].y+5 ;
            if(balls[i].y<=0 || balls[i].y+20>=this.getHeight()){
                balls[i].up=!balls[i].up;
            }
            //方法2：
//          balls[i].x+=5;//球被畫死了
//          balls[i].y+=5;
            g.fillOval(balls[i].x, balls[i].y, 20, 20);//畫實心球，直徑20,20
        }
    }
    public void actionPerformed(ActionEvent e) {？//監聽執行緒,每delay時間間隔畫一次球

        repaint();
    }

    public void focusGained(FocusEvent e) {//監聽焦點，點選畫布時停止

        timer.stop();
    }

    public void focusLost(FocusEvent e) {//監聽焦點，點選其他重新啟動，如微調按鈕編輯框

        timer.restart();
    }
}

結果顯示：