谁帮忙指导一下！

import java.applet.Applet; 
import java.awt.*; 
import java.awt.event.*; 
public class Sort extends Applet implements Runnable{ 
     public  static int[] data={18,4,17,5,13,8,14,7,10,16,11,3,19,2,20,15,6,9,1,12}; 
     Button bt=new Button("Start"); 
           int x=50,y=100; 
           Graphics g=getGraphics(); 
     public void init(){ 
          add(bt); 
          this.setSize(300,300);
          bt.addActionListener(new ActionListener(){ 
                  public void actionPerformed(ActionEvent e){ 
                             if(e.getSource()==bt)threadStart();
                 } 
          });
     } 
     public void threadStart(){
         new Thread(this).start();
     }
     public void paint(Graphics g){
           g.setColor(Color.green); 
           g.setFont(new Font("TimesRoman",Font.PLAIN,12)); 
          for(int k=-1;++k <data.length;){
                g.drawRect(x,y+10*k,10*data[k],5); 
                g.fillRect(x,y+10*k,10*data[k],5); 
                g.drawString(String.valueOf(data[k]),x+10*data[k]+15,y+10*(k+1)); 
              }
          }
     public void run() {
            sort(data);
            }
   public void sort(int a[]){ 
    for (int i = a.length; --i>=0;) 
      for (int j = 0; j <i; j++) {
          if (a[j] > a[j+1]) {
              int T = a[j];
              a[j] = a[j+1];
              a[j+1] = T;
              repaint();
              try {
                Thread.sleep(1000);
                  } catch (InterruptedException e) {
                      e.printStackTrace();
                  }
              }
          }
    }
}以上是实现排序过程的演示，大虾帮忙实现一下“暂停”和“继续”功能