匿名内部类-表达式的非法开始

Question

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

    public class Lab2Part2 extends JFrame implements ActionListener
    {  

   private JFrame frame;
   private JButton button;
   private JPanel panel;

   public Lab2Part2()
   {
      setLayout(new GridLayout());
      frame = new JFrame();
      button = new JButton("Let's start this show");
      panel = new JPanel();
      panel.add(button);

      InnerProgress prog1 = new InnerProgress("Progress 1: ");
      InnerProgress prog2 = new InnerProgress("Progress 2: ");

      button.addActionListener(new ActionListener());

      //this is where it throws errors
      public void actionPerformed(ActionEvent e)
      {  
      Object source = e.getSource();
      if(source == button)
      {
      Thread th1 = new Thread(prog1);
      Thread th2 = new Thread(prog2);
      th1.start();
      th2.start();
      }
   } 

  add(panel);
  add(prog1);
  add(prog2);   



  setVisible(true);
  setDefaultCloseOperation(EXIT_ON_CLOSE);
  setLocationRelativeTo(null);
  pack();
   }

   public static void main(String [] args)
   {
   new Lab2Part2();
   }  

   class InnerProgress extends JPanel implements Runnable
   {
   private String progress;
   private JProgressBar bar;

   public InnerProgress(String _progress)
   {
      progress = _progress;
      add(bar);
   }  

   public void run()
   {  
      System.out.println("We are running: " + progress);
   }
 }  
}

Answer 1

你把你的代码搞混了，结果是方法里面有方法。

          button.addActionListener(new ActionListener());

          //this is where it throws errors
          public void actionPerformed(ActionEvent e)
          {  
          Object source = e.getSource();
          if(source == button)
          {
          Thread th1 = new Thread(prog1);
          Thread th2 = new Thread(prog2);
          th1.start();
          th2.start();
          }
       } 

整个actionperformed方法实际上应该在一个匿名的内部类中，但事实并非如此。

      button.addActionListener(new ActionListener(){

      //this is where it throws errors
      public void actionPerformed(ActionEvent e)
      {  
      Object source = e.getSource();
      if(source == button)
      {
      Thread th1 = new Thread(prog1);
      Thread th2 = new Thread(prog2);
      th1.start();
      th2.start();
      }
   }); 

将方法保留在匿名实现中。