关于java图形界面的问题

Question

import java.awt.*;
import javax.swing.*;
public class test1 extends JFrame
{
JPanel mb1,mb2,mb3;
JButton an1,an2;
JLabel bq1,bq2;
JCheckBox fxk1,fxk2,fxk3;
JRadioButton dx1,dx2;
ButtonGroup dxz;
public static void main(String[]args){
test1 a=new test1();
}

test1()
{
mb1=new JPanel();
mb2=new JPanel();
mb3=new JPanel();
bq1=new JLabel("特长");
bq2=new JLabel("性别");
fxk1=new JCheckBox("音乐");
fxk2=new JCheckBox("体育");
fxk3=new JCheckBox("文艺");
dx1=new JRadioButton("男");
dx2=new JRadioButton("女");
dxz=new ButtonGroup();
dxz.add(dx1); dxz.add(dx2);
this.setLayout(new GridLayout(3,1));
mb1.add(bq1); mb1.add(fxk1); mb1.add(fxk2);mb1.add(fxk3);
mb2.add(bq2); mb2.add(dx1); mb2.add(dx2);
mb3.add(an1); mb3.add(an2);
this.add(mb1);
this.add(mb2);
this.add(mb3);
this.setTitle("用户注册");
this.setSize(240,150);
this.setLocation(300,280);
this.setResizable(false);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}
}

一直报错，Exception in thread "main" java.lang.NullPointerException
但是自检找不到问题出在哪里，希望大家能帮帮我，谢谢了

Answer 1

已经帮你改好了，，，看下面：

import java.awt.*;
import javax.swing.*;
 public class test1 extends JFrame
{
    JPanel mb1,mb2,mb3;
    JButton an1,an2;
    JLabel bq1,bq2;
    JCheckBox fxk1,fxk2,fxk3;
    JRadioButton dx1,dx2;
    ButtonGroup dxz;
    public static void main(String[]args){
        test1 a=new test1();
    }

    test1()
    {
        mb1=new JPanel();
        mb2=new JPanel();
        mb3=new JPanel();
        bq1=new JLabel("特长");
        bq2=new JLabel("性别");
        fxk1=new JCheckBox("音乐");
        fxk2=new JCheckBox("体育");
        fxk3=new JCheckBox("文艺");
        dx1=new JRadioButton("男");
        dx2=new JRadioButton("女");
        dxz=new ButtonGroup();
        dxz.add(dx1); dxz.add(dx2);
        an1 = new JButton("an1");
        an2 = new JButton("an2");
        this.setLayout(new GridLayout(3,1));
        mb1.add(bq1); mb1.add(fxk1); mb1.add(fxk2);mb1.add(fxk3);
        mb2.add(bq2); mb2.add(dx1); mb2.add(dx2);
        mb3.add(an1); mb3.add(an2);
        this.add(mb1);
        this.add(mb2);
        this.add(mb3);
        this.setTitle("用户注册");
        this.setSize(240,150);
        this.setLocation(300,280);
        this.setResizable(false);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
    }
}

给个采纳呗