Documentation Contents
Java Platform, Standard Edition Tools Reference
Contents Previous Next

# javap

Disassembles one or more class files.

## Synopsis

javap [options] classfile...

options

  The command-line options. See Options.

classfile

  One or more classes separated by spaces to be processed for annotations such as DocFooter.class. You can specify a class that can be found in the class path, by its file name or with a URL such as `file:///home/user/myproject/src/DocFooter.class`.

## Description

The `javap` command disassembles one or more class files. The output depends on the options used. When no options are used, then the `javap` command prints the package, protected and public fields, and methods of the classes passed to it. The `javap` command prints its output to `stdout`.

## Options

-help
--help
-?

  Prints a help message for the `javap` command.

-version

  Prints release information.

-l

  Prints line and local variable tables.

-public

  Shows only public classes and members.

-protected

  Shows only protected and public classes and members.

-private
-p

  Shows all classes and members.

-Joption

  Passes the specified option to the JVM. For example:

      javap -J-version
      javap -J-Djava.security.manager -J-Djava.security.policy=MyPolicy MyClassName

  For more information about JVM options, see the ``java`` command documentation.

-s

  Prints internal type signatures.

-sysinfo

  Shows system information (path, size, date, MD5 hash) of the class being processed.

-constants

  Shows `static final` constants.

-c

  Prints disassembled code, for example, the instructions that comprise the Java bytecodes, for each of the methods in the class.

-verbose

  Prints stack size, number of locals and arguments for methods.

-classpath path

  Specifies the path the `javap` command uses to look up classes. Overrides the default or the `CLASSPATH` environment variable when it is set.

-bootclasspath path

  Specifies the path from which to load bootstrap classes. By default, the bootstrap classes are the classes that implement the core Java platform located in `jre/lib/rt.jar` and several other JAR files.

-extdir dirs

  Overrides the location at which installed extensions are searched for. The default location for extensions is the value of `java.ext.dirs`.

## Example

Compile the following `DocFooter` class:

    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 the `javap DocFooter.class` command yields the following:

    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);
    }

The output from `javap -c DocFooter.class` command yields the following:

    Compiled from "DocFooter.java"
    public class DocFooter extends java.applet.Applet {
      java.lang.String date;
      java.lang.String email;

      public DocFooter();
        Code:
           0: aload_0
           1: invokespecial #1                  // Method
    java/applet/Applet."<init>":()V
           4: return

      public void init();
        Code:
           0: aload_0
           1: sipush        500
           4: bipush        100
           6: invokevirtual #2                  // Method resize:(II)V
           9: aload_0
          10: aload_0
          11: ldc           #3                  // String LAST_UPDATED
          13: invokevirtual #4                  // Method
     getParameter:(Ljava/lang/String;)Ljava/lang/String;
          16: putfield      #5                  // Field date:Ljava/lang/String;
          19: aload_0
          20: aload_0
          21: ldc           #6                  // String EMAIL
          23: invokevirtual #4                  // Method
     getParameter:(Ljava/lang/String;)Ljava/lang/String;
          26: putfield      #7                  // Field email:Ljava/lang/String;
          29: return

      public void paint(java.awt.Graphics);
        Code:
           0: aload_1
           1: new           #8                  // class java/lang/StringBuilder
           4: dup
           5: invokespecial #9                  // Method
     java/lang/StringBuilder."<init>":()V
           8: aload_0
           9: getfield      #5                  // Field date:Ljava/lang/String;
          12: invokevirtual #10                 // Method
     java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
          15: ldc           #11                 // String  by
          17: invokevirtual #10                 // Method
     java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
          20: invokevirtual #12                 // Method
     java/lang/StringBuilder.toString:()Ljava/lang/String;
          23: bipush        100
          25: bipush        15
          27: invokevirtual #13                 // Method
     java/awt/Graphics.drawString:(Ljava/lang/String;II)V
          30: aload_1
          31: aload_0
          32: getfield      #7                  // Field email:Ljava/lang/String;
          35: sipush        290
          38: bipush        15
          40: invokevirtual #13                 // Method
    java/awt/Graphics.drawString:(Ljava/lang/String;II)V
          43: return
    }

## See Also

- `java`(1)

- `javac`(1)

- `javadoc`(1)

- `javah`(1)

- `jdb`(1)

- `jdeps`(1)

Contents Previous Next

Copyright © 1993, 2015, Oracle and/or its affiliates. All rights reserved.
Contact Us