如何在java中更改球图形的颜色和类型

Question

package bouncetugas;

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


public class BounceTugas {

public static void main(String[] args) {
  EventQueue.invokeLater(new Runnable()
            {
                public void run()
                {
                    JFrame frame = new BounceFrame();
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.setVisible(true);
                }
            });
    }
}

/ **一个可运行的弹跳球动画* /

class BallRunnable implements Runnable 
{

    public BallRunnable(Ball aBall, Component aComponent)
    {
    ball = aBall;
    component = aComponent;
    }
public void run()
{
    try {
        for (int i = 1; i <= STEPS; i++)
        {
            ball.move(component.getBounds());
            component.repaint();
            Thread.sleep(DELAY);
        }
    }
    catch (InterruptedException e)
    {
    }
}

private Ball ball;

private Component component;

public static final int STEPS = 1000;

public static final int DELAY = 5;
}

//带面板和按钮的框架。

class BounceFrame extends JFrame
{

/ 使用要显示的组件构造框架 弹跳球和开始和关闭按钮 /

    public BounceFrame()
    {

    setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
    setTitle("Bounce Latihan");

    comp = new BallComponent();
    add(comp, BorderLayout.CENTER);
    JPanel buttonPanel = new JPanel();
     addButton(buttonPanel, "Add Ball", new ActionListener()
    {

        public void actionPerformed(ActionEvent event)
        {
            addBall();
        }
    });

      addButton(buttonPanel, "Remove Ball", new ActionListener()
    {
        public void actionPerformed(ActionEvent event)
        {
            addBall();
        }
    });
       addButton(buttonPanel, "Change Color", new ActionListener()
    {
        public void actionPerformed(ActionEvent event)
        {
            addBall();
        }
    });
        addButton(buttonPanel, "Change Type", new ActionListener()
    {
        public void actionPerformed(ActionEvent event)
        {
            addBall();
        }
    });
          addButton(buttonPanel, "Start", new ActionListener()
    {
        public void actionPerformed(ActionEvent event)
        {
            addBall();
        }
    });
         addButton(buttonPanel, "Pause", new ActionListener()
    {
        public void actionPerformed(ActionEvent event)
        {
            pauseBall();
        }
    });
         addButton(buttonPanel, "Close", new ActionListener()
    {
        public void actionPerformed(ActionEvent event)
        {
            System.exit(0);
        }
    });

    add(buttonPanel, BorderLayout.SOUTH);
}

//向容器添加按钮。

public void addButton(Container c, String title, ActionListener listener)
{

    JButton button = new JButton(title);
    c.add(button);
    button.addActionListener(listener);

}

//向画布添加一个弹跳球并启动一个线程使其反弹

public void addBall()
{
    Ball b = new Ball();
    comp.add(b);
    Runnable r = new BallRunnable(b, comp);
    Thread t = new Thread(r);
    t.start();
}

public void pauseBall()
{

//我不知道应该写什么代码

}

private BallComponent comp;
public static final int DEFAULT_WIDTH = 650;
public static final int DEFAULT_HEIGHT = 450;
public static final int STEPS = 1000;
public static final int DELAY = 3;
}

// package bouncetugas;

class Ball {

//将球移动到下一个位置， //如果碰到其中一条边，则反转方向

 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;
       }
   }

//获取球在当前位置的形状。

public Ellipse2D getShape()
{

return new Ellipse2D.Double(x,y, XSIZE, YSIZE);
}


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;
}

//绘制球的组件。

class BallComponent extends JPanel {

//将球添加到组件

public void add(Ball b)
{
   balls.add(b); 
}

public void paintComponent(Graphics g)
{

//擦除

    super.paintComponent(g); 
    Graphics2D g2 = (Graphics2D) g;
    for (Ball b : balls)
    {

        g2.fill(b.getShape());

    }
}
 private ArrayList<Ball> balls = new ArrayList<Ball>();
}