方法声明无效？ Return 类型需要吗？

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) 复制了代码，但我不确定问题出在哪里。感谢任何帮助:)

Answer 1

public Gui(); 没有任何 return 类型，也没有任何实现，它不应该在 QA

中

将此构造方法移至 Gui class

public class Gui extends JFrame{

public Gui(){}

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

方法声明无效？ Return 类型需要吗？

Invalid Method Declaration? Return Type Required?

java

button

bluej