import java.awt.*;import java.awt.event.*;import javax.swing.*;public class GoodLucky extends JFrame implements ActionListener{  JTextField tf = new JTextField(); JButton b1 = new JButton("开始"); JButton b2 = new JButton("停止"); boolean isGo = false; public GoodLucky(){  b1.setActionCommand("start");    JPanel p = new JPanel();  p.add(b1);  p.add(b2);      b1.addActionListener(this);  b2.addActionListener(this);  b2.setEnabled(false);    this.getContentPane().add(tf,"North");  this.getContentPane().add(p,"South");  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  this.setSize(300,200);  this.setLocation(300,300);  Cursor cu = new Cursor(Cursor.HAND_CURSOR);  this.setCursor(cu);  this.setVisible(true);  tf.setText("welcome you!                  ");  this.go();   }  public void go(){  while(true){   if(isGo == true){    String s = "";    for(int j = 1; j <= 7;j++){     int i = (int)(Math.random() * 33) + 1;     if(i < 10){      s = s + "  0" + i;     }else{      s = s + "  " + i;     }         }    tf.setText(s);   }      try{    Thread.sleep(10);   }catch(java.lang.InterruptedException e){    e.printStackTrace();   }     }   }     public void actionPerformed(ActionEvent e){  String s = e.getActionCommand();  if(s.equals("start")){   isGo = true;   b1.setEnabled(false);   b2.setEnabled(true);  }else{   isGo = false;   b2.setEnabled(false);   b1.setEnabled(true);  }   }    public static void main(String[] args){  new GoodLucky();   }}