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javap - Unix, Linux Command

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NAME

javap - Java class file disassembler

SYNOPSIS

javap [ options ] class ...

DESCRIPTION

The javap command disassembles a Java class file. The options determine the output. If no options are used, javap prints out the package, protected, and public fields and methods of the classes passed to it. The javap command displays 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();
}

OPTIONS

The following options are supported:
TagDescription
-b Ensures backward compatibility with javap in JDK 1.1.
-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/charsets.jar.
-c Prints out disassembled code, that is, the instructions that comprise the Java bytecodes, for each of the methods in the class. These are documented in the Java Virtual Machine Specification.
-classpathpath 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 colons (:). Thus the general format for path is:

TagDescription
  .:<your_path>

For example:

TagDescription
  .:/home/avh/classes:/usr/local/java/classes

TagDescription
-extdirsdirs Overrides location at which installed extensions are searched. The default location for extensions is jre/lib/ext.
-help Prints out help message for javap.
-Jflag Passes flag directly to runtime system.

javap -J-version

javap -JJ-Djava.security.manager \
-Djava.security.policy=MyPolicy MyClassName

-l Displays line and local variable tables.
-package Shows only package, protected, and public classes and members. This is the default.
-private Shows all classes and members.
-protected Shows only protected and public classes and members.
-public Shows only public classes and members.
-s Displays internal type signatures.
-verbose Prints stack size, number of locals, and args for methods.

ENVIRONMENT VARIABLES

TagDescription
CLASSPATH Used to provide the system with a path to user-defined classes. Directories are separated by colons. For example:

TagDescription
  .:/home/avh/classes:/usr/local/java/classes

SEE ALSO


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