Java从按钮不能连接到相应的界面

package FaultDiagnose;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.TitledBorder;

public class YeYaMain extends JFrame implements ActionListener{
private static final long serialVersionUID = 1L;


JButton jb2 = new JButton(" 一 因  一  果      ");
JButton jb8 = new JButton("非一因一果关系");
JButton jb6 = new JButton(" 返  回  上  层      ");
JButton jb7 = new JButton(" 退  出  系  统      ");

TitledBorder tb1=new TitledBorder("请选择");


JLabel jl1=new JLabel("欢迎"); 


//创建横向Box容器
private Box box0=Box.createVerticalBox();
private Box box1=Box.createHorizontalBox(); 
private Box box2=Box.createHorizontalBox();
private Box box3=Box.createVerticalBox();
private Box box4=Box.createVerticalBox();

  public YeYaMain(){
super("欢迎");




jb2.setSize(150,25);
jb6.setSize(150,25);

//加入图片
jl1.setBounds(150,100,1000,700); // 设置标签的显示位置及大小
jl1.setFont(new Font("", Font.BOLD, 28)); 


//加入下拉列表
this.add(box0);
box0.add(Box.createVerticalStrut(30));
box0.add(box1);

    box1.add(jl1);
box0.add(Box.createVerticalStrut(15));
box0.add(box2);
box2.add(Box.createHorizontalGlue());
box2.add(box3);
box3.setBorder(new TitledBorder(tb1));



box3.add(Box.createVerticalStrut(22));
box3.add(jb2);
jb2.addActionListener(this);

box3.add(Box.createHorizontalGlue());
box3.add(Box.createVerticalStrut(22));
box3.add(jb8);
    jb8.addActionListener(this);

box3.add(Box.createHorizontalGlue());
box3.add(Box.createVerticalStrut(22));
box3.add(jb6);
    jb6.addActionListener(this);
    box3.add(Box.createHorizontalGlue());
box3.add(Box.createVerticalStrut(22));
box3.add(jb7);
    jb7.addActionListener(this);
    
    
   
   

       
    
    box3.add(Box.createVerticalStrut(60));
    box2.add(Box.createHorizontalGlue());
box2.add(box4);//添加图片
box2.add(Box.createHorizontalGlue());
box0.add(Box.createVerticalStrut(22));

this.setVisible(true);
this.setResizable(false);
    this.setBounds(450,60,720,450);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }

  public void actionPerformed(ActionEvent e) {
  if(e.getSource() == jb2){
  HuiMain frame=new HuiMain();
  frame.setVisible(true);
  this.setVisible(false);
  }    
 
  if(e.getSource() == jb8){
  //DuoxitongMain frame=new DuoxitongMain();
  //frame.setVisible(true);
  this.setVisible(false);
  new DuoxitongMain();
  }

      if (e.getSource() == jb6){
      this.setVisible(false);
      new Main2();
         }
     
   
      else 
         if (e.getSource() ==jb7 ){ //退出系统
           System.exit(0);
       }
   
 }
}

[解决办法]
DuoxitongMain需要继承JFrame