javap - The Java Class File Disassembler

The complete explanation is available @ http://download.oracle.com/javase/1.5.0/docs/tooldocs/windows/javap.html

The javap command disassembles a class file. Its output depends on the options used. If no options are used, javap prints out the package, protected, and public fields and methods of the classes passed to it. javap prints its output to stdout. For example, compile the following class declaration:

import java.awt.*;
   import java.applet.*;

   public class DocFooter extends Applet {
        String date;
        String email;

        public void init() {
                resize(500,100);
                date = getParameter("LAST_UPDATED");
                email = getParameter("EMAIL");
        }

        public void paint(Graphics g) {
                g.drawString(date + " by ",100, 15);
                g.drawString(email,290,15);
        }
   }

The output from javap DocFooter yields:

Compiled from DocFooter.java
public class DocFooter extends java.applet.Applet {
    java.lang.String date;
    java.lang.String email;
    public DocFooter();
    public void init();
    public void paint(java.awt.Graphics);
}