java小球弹性碰撞

源码：

package E3;


import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Panel;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
public class drawBall4_3 extends Panel implements Runnable, KeyListener {


    private double x;
 double  dx;
    private double y;
 double dy;
    private double x2,dx2;
    private double y2,dy2;
    private double diameter;
    private int width=400;
    private int height=400;
    private Image im;
    private int xdirection=2,ydirection=2;
   
   
    private int xdirection2=2,ydirection2=2;
  
   
   
    public drawBall4_3() {
     x=5;
        y=50;
        dx=2;
        dy=2;
       
        x2=100;
        y2=10;
        dx2=1;
        dy2=1;
        diameter=30;
      
        setBackground(Color.pink);
        setPreferredSize(new Dimension(width, height));
        addKeyListener(this);
    }
    public void gameStart(){
     Thread gamethread = new Thread(this);
        gamethread.start();
    }
    public void gamePaint() {//前屏显示
        Graphics g;
        g = this.getGraphics();
        g.drawImage(im, 0, 0, null);//从后屏复制到前屏
        g.dispose();//释放当前屏幕Graphcis对象
    }
   
   
    public void gameRender() {//离屏绘制
     
     im = createImage(this.getWidth() , this.getHeight());//建立image对象
     Graphics dbg = im.getGraphics();//获取Graphics对象
        dbg.setColor(Color.pink);//设置绘图属性
        dbg.fillRect(0, 0,width , height);
      
        dbg.setColor(Color.blue);
       dbg.fillOval((int)x, (int)y,(int)diameter,(int)diameter);//绘制图形
       
        dbg.setColor(Color.yellow);
        dbg.fillOval((int)x2, (int)y2,(int)diameter,(int)diameter);//绘制图形
    }
    public void gameUpdate() {
     x+=dx;
     y+=dy;
     x2+=dx2;
     y2+=dy2;
      if(y<0)
       dy=-dy;
     if(y+30>400)
       dy=-dy;
     if(x<0)
      dx=-dx;
     if(x+30>400)
      dx=-dx;
      if(x2<0)
       dx2=-dx2;
     if(x2+30>400)
      dx2=-dx2;
      if(y2<0)
       dy2=-dy2;
     if(y2+30>400)
      dy2=-dy2;
     
     
    if ((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y) <= diameter*diameter) //当两球间的距离小于直径时，可认为两小球发生了碰撞
 {
  double degree = Math.atan((y - y2) / (x - x2)); //获取自己与发生碰撞的小球之间所形成的夹角，因为夹角只能在-pi/2-pi/2之间，所以还需判断两球的x坐标之间的关系
  if (x > x2)  //如果自己的x坐标大于发生碰撞的小球的x坐标，由数学知识可知自己应该往正向运动
  {
   dx = Math.cos(degree); 
   dy = Math.sin(degree);
   x+=dx;
      y+=dy;
      x2+=dx2;
      y2+=dy2;
  }
  else //如果自己的x坐标小于发生碰撞的小球的x坐标，由数学知识可知应该朝负向运动
  {
   dx =-Math.cos(degree);
   dy = -Math.sin(degree);
   x+=dx;
      y+=dy;
      x2+=dx2;
      y2+=dy2;
  }
 
       double degree1 = Math.atan((y2- y) / (x2 - x)); //获取自己与发生碰撞的小球之间所形成的夹角，因为夹角只能在-pi/2-pi/2之间，所以还需判断两球的x坐标之间的关系
  if (x2 > x)  //如果自己的x坐标大于发生碰撞的小球的x坐标，由数学知识可知自己应该往正向运动
  {
   dx2 = Math.cos(degree); 
   dy2= Math.sin(degree);
   x+=dx;
      y+=dy;
      x2+=dx2;
      y2+=dy2;
  }
  else //如果自己的x坐标小于发生碰撞的小球的x坐标，由数学知识可知应该朝负向运动
  {
   dx2 =-Math.cos(degree);
   dy2 =-Math.sin(degree);
   x+=dx;
      y+=dy;
      x2+=dx2;
      y2+=dy2;
  }}
    }
  
    public void run() {
        while(true){
           gameUpdate();
           gameRender();
           gamePaint();
           }
    }
 @Override
 public void keyPressed(KeyEvent arg0) {
  // TODO Auto-generated method stub
  
 }
 @Override
 public void keyReleased(KeyEvent arg0) {
  // TODO Auto-generated method stub
  
 }
 @Override
 public void keyTyped(KeyEvent arg0) {
  // TODO Auto-generated method stub
  
 }}

package E3;


import java.awt.BorderLayout;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
public class GameFrame4_3 {
    public GameFrame4_3() {
        JFrame app = new JFrame("GameFrame4_3");
        app.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        app.setLocation(100, 100);
       app.setLocationRelativeTo(null);
       
        drawBall4_3 drawB = new drawBall4_3();
        app.add(drawB);
       app.add(drawB, BorderLayout.CENTER);
        app.pack();
        app.setVisible(true);
        drawB.gameStart();
    }
    public static void main(String[] args) {
        new GameFrame4_3();
  
    }
}