什么是1美元的类文件名？ [英] What is the $1 in class file names?

问题描述

C:\Program Files\Java\jdk1.6.0_05\CoreJava\v1\v1ch2\WelcomeApplet>dir
 Volume in drive C has no label.
 Volume Serial Number is 2041-64E7

 Directory of C:\Program Files\Java\jdk1.6.0_05\CoreJava\v1\v1ch2\WelcomeApplet

2009-07-02  23:54              .
2009-07-02  23:54              ..
2004-09-06  14:57               582 WelcomeApplet.html
2004-09-06  15:04             1,402 WelcomeApplet.java
               2 File(s)          1,984 bytes
               2 Dir(s)   2,557,210,624 bytes free

C:\Program Files\Java\jdk1.6.0_05\CoreJava\v1\v1ch2\WelcomeApplet>javac WelcomeApplet.java

C:\Program Files\Java\jdk1.6.0_05\CoreJava\v1\v1ch2\WelcomeApplet>dir
 Volume in drive C has no label.
 Volume Serial Number is 2041-64E7

 Directory of C:\Program Files\Java\jdk1.6.0_05\CoreJava\v1\v1ch2\WelcomeApplet

2009-07-02  23:54              .
2009-07-02  23:54              ..
2009-07-02  23:54               975 WelcomeApplet$1.class
2009-07-02  23:54             1,379 WelcomeApplet.class
2004-09-06  14:57               582 WelcomeApplet.html
2004-09-06  15:04             1,402 WelcomeApplet.java
               4 File(s)          4,338 bytes
               2 Dir(s)   2,557,202,432 bytes free

C:\Program Files\Java\jdk1.6.0_05\CoreJava\v1\v1ch2\WelcomeApplet>

以下是该Java文件的内容：

Here is the content of that Java file:

/**
   @version 1.21 2002-06-19
   @author Cay Horstmann
*/

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

public class WelcomeApplet extends JApplet
{
   public void init()
   {
      setLayout(new BorderLayout());

      JLabel label = new JLabel(getParameter("greeting"), SwingConstants.CENTER);
      label.setFont(new Font("Serif", Font.BOLD, 18));
      add(label, BorderLayout.CENTER);

      JPanel panel = new JPanel();

      JButton cayButton = new JButton("Cay Horstmann");
      cayButton.addActionListener(makeURLActionListener(
         "http://www.horstmann.com"));
      panel.add(cayButton);

      JButton garyButton = new JButton("Gary Cornell");
      garyButton.addActionListener(makeURLActionListener(
         "mailto:[e-mail]"));
      panel.add(garyButton);

      add(panel, BorderLayout.SOUTH);
   }

   private ActionListener makeURLActionListener(final String u)
   {
      return new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               try
               {
                  getAppletContext().showDocument(new URL(u));
               }
               catch(MalformedURLException e) 
               { 
                  e.printStackTrace(); 
               }
            }
         };
   }
}

推荐答案

那些是包含匿名内部类<的 .class 文件/ a>。

Those are the .class files that hold the anonymous inner classes.

在您的示例中 WelcomeApplet.java 包含一个顶级类（称为 WelcomeApplet ）和一个匿名内部类，它将存储在 WelcomeApplet $ 1.class 中。

In your example WelcomeApplet.java contains a top-level class (called WelcomeApplet) and an anonymous inner class, which will be stored in WelcomeApplet$1.class.

请注意，包含匿名内部类的文件的确切名称不是标准化的，可能会有所不同。但实际上我还没有看到任何其他方案，而不是这里描述的方案。

Note that the exact name of the files holding anonymous inner classes is not standardized and might vary. But in practice I've yet to see any other scheme than the one described here.

enum的值特定主体 也是匿名的内心类：

枚举常量的可选类体隐式定义一个匿名类声明（§15.9.5）延伸立即封闭枚举类型。

The optional class body of an enum constant implicitly defines an anonymous class declaration (§15.9.5) that extends the immediately enclosing enum type.

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