线程中断问题

帮我改一下这两道中断程序，能够启动，但是不能中断。麻烦修改过的发上来，谢谢！import java.awt.*;
import java.awt.event.*;
public class Welcome extends WindowAdapter implements ActionListener
{
    Frame f;
    static Welcome.Thread3 wt1,wt2;
    public static void main(String arg[])
    {
        Welcome w= new Welcome();
        w.display();
        wt1=w.new Thread3("Welcome!");
        wt2=w.new Thread3("How are you?");
        wt2.start();
        wt2.setButton();                 //设置按钮状态
    }
    public void display()
    {
        f = new Frame("Welcome");
        f.setSize(400,240);
        f.setLocation(200,140);
        f.setBackground(Color.lightGray);
        f.setLayout(new GridLayout(4,1));
        f.addWindowListener(this);
        f.setVisible(true);
    }
    public class Thread3 extends Thread
    {
        Panel p1;
        Label lb1;
        TextField tf1,tf2;
        Button b1,b2;
        int sleeptime = (int)(Math.random()*100);
        public Thread3(String str)
        {
            super(str);
            for(int i=0;i<100;i++)
                str = str + " ";
            tf1 = new TextField(str);
            f.add(tf1);
            p1 = new Panel();
            p1.setLayout(new FlowLayout(FlowLayout.LEFT));
            lb1 = new Label("sleep");
            tf2 = new TextField(""+sleeptime);
            p1.add(lb1);
            p1.add(tf2);
            b1 = new Button("启动");
            b2 = new Button("中断");
            p1.add(b1);
            p1.add(b2);
            b1.addActionListener(new Welcome());
            b2.addActionListener(new Welcome());
            f.add(p1);
            f.setVisible(true);
        }
        public void run()
        {
            String str;
            while(true)
            {
          //  while (this.isAlive() && !this.isInterrupted())
           // {                                    //线程活动且没中断时
                try
                {
                    str = tf1.getText();
                    str = str.substring(1)+ str.substring(0,1);
                    tf1.setText(str);
                   this.sleep(sleeptime);
                }
                catch(InterruptedException e)
                {                                //中断时抛出
                    System.out.println(e);
                    //break;                       //退出循环
                }
            }
        }
        public  void setButton()                 //设置按钮状态
        {
            if (this.isAlive())         b1.setEnabled(false);
            else b1.setEnabled(true);
            if (this.isInterrupted())   b2.setEnabled(false);
            else b2.setEnabled(true);
        }
    }//线程
    public void windowClosing(WindowEvent e)
    {
        System.exit(0);
    }
    public void actionPerformed(ActionEvent e)
    {                                            //单击按钮时触发
        if ((e.getSource()==wt1.b1) || (e.getSource()==wt1.b2))
            actionPerformed(e,wt1);
        if ((e.getSource()==wt2.b1) || (e.getSource()==wt2.b2))
            actionPerformed(e,wt2);
    }
    public void actionPerformed(ActionEvent e,Thread3 wt1)
    {                                            //重载
        if(e.getSource()==wt1.b1)                //启动
        {
            wt1.sleeptime=Integer.parseInt(wt1.tf2.getText());
            wt1.start();
        }
        if(e.getSource()==wt1.b2)                //中断
            wt1.interrupt();
        wt1.setButton();                         //设置按钮状态
    }
}
这是另外一道import java.awt.*;
import java.awt.event.*;
public class 暂停线程 extends Frame implements Runnable,ActionListener{
  Frame f;
  Button b1,b2,b3,b4;
  Label l;
  int x,y;
  Thread T;
  Boolean Tag;              ///应该改为boolean
  static 暂停线程 nc;
    public static void main(String[] args) {
        nc=new 暂停线程();
        nc.display();
    }
    public void display(){
        f=new Frame();
        f.setLayout(null);
        b1=new Button("开始");
        b1.setBounds(20, 20, 50, 30);
        b2=new Button("暂停");
        b2.setBounds(80,20,50,30);
        b1.addActionListener(this);
        b2.addActionListener(this);
        b1.setEnabled(true);
        b2.setEnabled(false);
        f.add(b1);
        f.add(b2);
        l=new Label("我是标签");
        l.setBounds(20,60,50,50);
        f.add(l);
        f.setBounds(10, 10, 300, 200);    //窗体大小
        f.setVisible(true);
        f.addWindowListener(new WindowAdapter(){
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }
        });
    }
    public void actionPerformed(ActionEvent e1){
        if (e1.getSource()==b1){
            try{
            T=new Thread(nc);
            T.start();
            }
            catch(Exception e3){}
            Tag=true;
            b1.setEnabled(false);
            b2.setEnabled(true);
        }
        if(e1.getSource()==b2){
            Tag=false;
            b2.setEnabled(false);
            b1.setEnabled(true);
        }
    }
   public void run(){
         while(true)
         {
           if(Tag){
           x=l.getBounds().x;
           y=l.getBounds().y;
           x=x+2;
           y=y+2;
           if (x>250) x=20;
           if (y>150) y=60;
           l.setLocation(x,y);
           try
           {
               T.sleep(200);
           }
              catch(Exception e2){}
         }
         }
       }
   }