tf.setBounds(80,90, 200, 200); 把90改成91试试

import java.awt.*;
import java.awt.event.*;
import java.util.Random;

import javax.swing.*;

public class Three extends JFrame implements ActionListener{

/**
 * 
 */
private static final long serialVersionUID = -8560277451929244119L;
JTextField tf = new JTextField();
JButton b1 = new JButton("开始");
JButton b2 = new JButton("停止");
JButton b3 = new JButton("END");
boolean isGo = false;

public Three() {
    this.getContentPane().setLayout(null);
    this.setExtendedState(JFrame.MAXIMIZED_BOTH);

    tf.setBounds(80,90, 200, 200);
    b1.setBounds(1,100,10,10);
    b2.setBounds(1,200,10,10);
    b3.setBounds(1,300,10,10);

    this.getContentPane().add(tf);
    this.getContentPane().add(b1);
    this.getContentPane().add(b2);
    this.getContentPane().add(b3);



    b1.addActionListener(this);
    b2.addActionListener(this);
    b3.addActionListener(this);

    SymListener sy = new SymListener();
    b1.registerKeyboardAction(sy,KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), JComponent.WHEN_IN_FOCUSED_WINDOW); 
    b2.registerKeyboardAction(sy,KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), JComponent.WHEN_IN_FOCUSED_WINDOW); 
    b3.registerKeyboardAction(sy,KeyStroke.getKeyStroke(KeyEvent.VK_Q, 0), JComponent.WHEN_IN_FOCUSED_WINDOW); 

    b2.setEnabled(false);

    this.setVisible(true);
    tf.setText("888888");
    go();

}    

public void go() {
    while (true) {
        if (isGo == true) {
            String s = "";

            for (int j = 1; j <= 1; j++) {
                int i = (int) (Math.random()*10000+1);//设定奖项总数
                if (i < 10) {
                    s = s + "00000" + i;
                } else if(i<100 & i>=10) 
                {
                    s = s + "0000" + i;
                }else if(i<1000 & i>=100) 
                {
                    s = s + "000" + i;
                }else if(i<10000 & i>=1000) 
                {
                    s = s + "00" + i;
                }else if(i<100000 & i>=10000) 
                {
                    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) {

}

public static void main(String[] args)  {

    new Three();

} 
class SymListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
    Object obj = e.getSource();

    if (obj == b1) {
            isGo = true;
            b1.setEnabled(false);
            b2.setEnabled(true);
    } else if (obj == b2) {
        isGo=false;
        b2.setEnabled(false);
        b1.setEnabled(true);


    }else if (obj == b3) {
        dispose();

    }
    }
    }

}

我为什么要改呢？为什么呢？

改后在按空格 看数字变不变 为什么不变了。 BUG吗？ 如果把 KeyEvent.VK_SPACE, 换成别的快捷键就没问题

修改一
 //b1.registerKeyboardAction(sy,KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0), JComponent.WHEN_IN_FOCUSED_WINDOW); //搜索这句，然后注释，增加下面，其他按钮也可以一样处理
 b1.getInputMap(JComponent.WHEN_FOCUSED).put(
         KeyStroke.getKeyStroke((char)KeyEvent.VK_SPACE), "PressKeyAction");
   b1.getActionMap().put("PressKeyAction", new AbstractAction() {
        public void actionPerformed(ActionEvent e) {
            isGo = true;
               b1.setEnabled(false);
               b2.setEnabled(true);
        }
       });
修改二
this.setVisible(true);
    tf.setText("888888");//搜索这句

    b1.requestFocus();//增加获取焦点