java异常

Question

import java.awt.*;
import javax.swing.*;
public class FlowLayoutDemo{
private JFrame frame;
private JButton button1,button2,button3;public static void main(String args[]){
FlowLayoutDemo that=new FlowLayoutDemo();
that.go();
}
public void go(){
frame=new JFrame("flowLayout");
Container contentPane=frame.getContentPane();
contentPane.setLayout(new FlowLayout());button1=new JButton("Yes");
button1=new JButton("No");
button1=new JButton("Cancle");contentPane.add(button1);
contentPane.add(button2);                          
contentPane.add(button3);frame.setSize(200,100);
frame.setVisible(true);
}
}
这个程序编译可通过,便运行时不行,请高手门帮忙,十分感谢!

Answer 1

button1=new JButton("Yes"); 
button2=new JButton("No"); 
button3=new JButton("Cancle");