高手帮忙 救救我 在线等 指教我那里不对 然后帮我改下 谢谢
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;

/**
  Shouws an animated bouncing ball.
  */
  public class BounceThread
  {
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 the edges of a rectangle
*/
class BallRunable implements Runnable
{
/**
Constructs the runnable.
@aBall the ball to bounce 
@aPanel the component in which the ball bounces
*/
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;


}

class Ball
{
/** 
moves the ball to the next position, reversing direction
if it hits one of the edges
*/
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);
}
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;
}

/**
  The panel that draws the balls.
  */
class BallPanel extends JPanel
{
/** 
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;
for (Ball b : balls )
{
g2.fill(b.getShape());
}
}
private ArrayList<Ball> balls = new ArrayList<Ball>();
}

/**
  The frame with panel and buttons.
  */
class BounceFrame extends JFrame
{
/**
Constructs the frame with the panel for showing the
bouncing ball and Start and Close buttons
*/
  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);
  }
/**
Adss a button to a container.