phpman > man > javap(1)

javap(1)                                     Basic Tools                                    javap(1)



NAME
       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 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)



JDK 8                                       8 August 2014                                   javap(1)