无效的方法声明？要求退货类型？

Question

import java.util.*;
import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JOptionPane;
//----------I could just do import java.awt.*; and import java.swing.*; but, when the program get larger, this could cause glitches, so it's better not to----------
public class Gui extends JFrame{

public class QA //THIS IS WHERE I'M GETTING THE ERROR MESSAGE
{
    private int x;
         private JButton reg;
         private JButton custon;

         public Gui();
    public QA()
    {

我从YouTube视频（https://www.youtube.com/watch?v=6iV-v_m0z0w）中删除了代码，但我不确定问题是什么。感谢任何帮助：）

Answer 1

public Gui();没有任何退货类型且没有任何实施，且它不应该在QA

内

将此构造函数方法移至Gui class

public class Gui extends JFrame{

public Gui(){}

public class QA //THIS IS WHERE I'M GETTING THE ERROR MESSAGE
{
...
}