java虚拟机

1.javap -c 文件名 进行反编译

代码：

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

/**
 * A program for viewing images.
 * @version 1.31 2018-04-10
 * @author Cay Horstmann
 */
public class ImageViewer
{
   public static void main(String[] args)
   {
      EventQueue.invokeLater(() -> {
         var frame = new ImageViewerFrame();
         frame.setTitle("ImageViewer");
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setVisible(true);
      });
   }
}

/**
 * A frame with a label to show an image.
 */
class ImageViewerFrame extends JFrame
{
   private static final int DEFAULT_WIDTH = 300;
   private static final int DEFAULT_HEIGHT = 400;

   public ImageViewerFrame()
   {
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

      // use a label to display the images
      var label = new JLabel();
      add(label);

      // set up the file chooser
      var chooser = new JFileChooser();
      chooser.setCurrentDirectory(new File("."));

      // set up the menu bar
      var menuBar = new JMenuBar();
      setJMenuBar(menuBar);

      var menu = new JMenu("File");
      menuBar.add(menu);

      var openItem = new JMenuItem("Open");
      menu.add(openItem);
      openItem.addActionListener(event -> {
         // show file chooser dialog
         int result = chooser.showOpenDialog(null);

         // if file selected, set it as icon of the label
         if (result == JFileChooser.APPROVE_OPTION)
         {
            String name = chooser.getSelectedFile().getPath();
            label.setIcon(new ImageIcon(name));
         }
      });

      var exitItem = new JMenuItem("Exit");
      menu.add(exitItem);
      exitItem.addActionListener(event -> System.exit(0));
   }
}

反编译结果：

Compiled from "ImageViewer.java"
public class ImageViewer {
  public ImageViewer();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return

  public static void main(java.lang.String[]);
    Code:
       0: invokedynamic #2,  0              // InvokeDynamic #0:run:()Ljava/lang/Runnable;
       5: invokestatic  #3                  // Method java/awt/EventQueue.invokeLater:(Ljava/lang/Runnable;)V
       8: return
}

todo

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