为什么我的程序运行不了。。。求大神帮忙

Question

package 跑;

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.event.*;

public class JinZhi extends JFrame implements ActionListener{

JLabel jl1,jl2,jl3,jl4;
JTextField jt1,jt2,jt3,jt4;

public JinZhi(){
    super("十进制转换");
    setBounds(200,100,200,100);
    setLayout(new GridLayout(4,2));
    add(new JLabel("十进制"));
    jt1=new JTextField("1023");
    jt1.addActionListener(this);
    add(jt1);
    add(new JLabel("二进制"));
    jt2=new JTextField("1111111111");
    jt2.setEditable(false);
    add(jt2);
    add(new JLabel("八进制"));
    jt3=new JTextField("1777");
    jt3.setEditable(false);
    add(jt3);
    add(new JLabel("十六进制"));
    jt3=new JTextField("3ff");
    jt4.setEditable(false);
    add(jt4);
    setVisible(true);

}
public void actionPerformed(ActionEvent e) {
    String s=jt1.getText();
    int a=Integer.parseInt(s);
    jt2.setText(Integer.toBinaryString(a)); 
    jt3.setText(Integer.toOctalString(a));
    jt4.setText(Integer.toHexString(a));

}
public static void main(String []args){
    new JinZhi();
}

}

Answer 1

jt3=new JTextField("3ff");
应该是jt4