javap - The Java Class File Disassembler

Disassembles class files.

SYNOPSIS

   javap [ options ] class. . .

DESCRIPTION

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 void init();
       public void paint(java.awt.Graphics);
       public DocFooter();
   }

-help

Prints out help message for javap.

-l

Prints out line and local variable tables.

-b

Ensures backward compatibility with javap in JDK 1.1.

-public

Shows only public classes and members.

-protected

Shows only protected and public classes and members.

-package

Shows only package, protected, and public classes and members. This is the default.

-private

Shows all classes and members.

-Jflag

Pass flag directly to the runtime system. Some examples:

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

-s

Prints internal type signatures.

-c

Prints out disassembled code, i.e., the instructions that comprise the Java bytecodes, for each of the methods in the class. These are documented in the Java Virtual Machine Specification.

-verbose

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

-classpath path

Specifies the path javap uses to look up classes. Overrides the default or the CLASSPATH environment variable if it is set. Directories are separated by semi-colons. Thus the general format for path is:

   .;<your_path>

For example:

   .;C:\usrs\dac\classes;C:\tools\java\classes

-bootclasspath path

Specifies path from which to load bootstrap classes. By default, the bootstrap classes are the classes implementing the core Java platform located in jre\lib\rt.jar and jre\lib\i18n.jar.

-extdirs dirs

Overrides location at which installed extensions are searched for. The default location for extensions is jre\lib\ext.

ENVIRONMENT VARIABLES

CLASSPATH

Used to provide the system a path to user-defined classes. Directories are separated by semi-colons, for example, For example:

   .;C:\usrs\dac\classes;C:\tools\java\classes

SEE ALSO

javac, java, jdb, javah