java多线程，三个按钮的移动实现问题

Question

import java.awt.*;
import java.awt.event.*;
public class moveButton extends Frame implements Runnable,ActionListener
{
Thread  first,second,third;
Button redbutton,greenbutton,yellowbutton,startbutton;
int distance=10;
moveButton()
{
first=new Thread(this);
second=new Thread(this);
third=new Thread(this);

redbutton=new Button();
greenbutton=new Button();
yellowbutton=new Button();

redbutton.setBackground(Color.red);
greenbutton.setBackground(Color.green);
yellowbutton.setBackground(Color.yellow);

startbutton=new Button("star");
startbutton.addActionListener(this);
setLayout(null);

add(redbutton);
redbutton.setBounds(10,60,15,15);
add(greenbutton);
greenbutton.setBounds(100,60,15,15);
add(yellowbutton);
yellowbutton.setBounds(200,60,15,15);
add(startbutton);
startbutton.setBounds(10,100,30,30);
setBounds(0,0,300,200);
setVisible(true);
validate();
}
public void actionPerformed(ActionEvent e)
{
try
{

first.start();
second.start();
third.start();
}
catch(Exception exp){}
}
public void run()
{

while(true)
{

if(Thread.currentThread()==first)
{
moveComponent(redbutton);
try
{
Thread.sleep(20);
}
catch(Exception exp){}
}
if(Thread.currentThread()==second)
{
moveComponent(greenbutton);
try
{
Thread.sleep(10);
}
catch(Exception exp){}
}
if(Thread.currentThread()==third)
{
moveComponent(yellowbutton);
try
{
Thread.sleep(5);
}
catch(Exception exp){}
}

}

}
public synchronized void moveComponent(Component b)
{
if(Thread.currentThread()==first)
{
while(distance>100&&distance<=300)
try{
wait();
}catch(Exception exp){}
distance=distance+1;
b.setLocation(distance,60);

if(distance>=100)
{
 b.setLocation(10,60);
 notifyAll();
}
}
if(Thread.currentThread()==second)
{
while(distance>=10&&distance<100||distance>=200&&distance<300)
try{
wait();
}catch(Exception exp){}
distance=distance+1;
b.setLocation(distance,60);

if(distance>200)
{
 //distance=200;
 b.setLocation(100,60);
 notifyAll();
}
}

if(Thread.currentThread()==third)
{
while(distance>=10&&distance<200)
try{
wait();
}catch(Exception exp){}
distance=distance+1;
b.setLocation(distance,60);

if(distance>300)
{
 distance=10;
 b.setLocation(200,60);
 notifyAll();
}
}
}

}public class Move
{
public static void main(String args[])
{
new moveButton();
}
}
老师布置的作业，三个按钮，第一个红的先运动10-100，碰到第二个绿色的按钮，红色的回到10，绿色的运动100-200，碰到第三个黄色的，绿色的回到200，黄色的运动200-300，然后回到200.然后这样循环。start按钮开始。我做的只有前两个按钮，四三个怎么不显示呢

Answer 1

 if(Thread.currentThread()==second)
        {
            while(distance>=10&&distance<100||distance>=200&&distance<300)
            try{
                wait();
            }catch(Exception exp){}
            distance=distance+1;
            b.setLocation(distance,60);
        
            if(distance>=200)
            {
             //distance=200;
             b.setLocation(100,60);
             notifyAll();    
            }
        }

Answer 2

还要把
//distance=200
注释去掉

Answer 3

//distance=200; 
注释去掉