JAVAP(1)                         JDK Commands                         JAVAP(1)

NAME
       javap - disassemble one or more class files

SYNOPSIS
       javap [options] classes...

       options
              Specifies the command-line options.  See Options for javap.

       classes
              Specifies one or more classes separated by spaces to be
              processed for annotations.  You can specify a class that can be
              found in the class path by its file name, URL, or by its fully
              qualified class name.

              Examples:

                     path/to/MyClass.class

                     jar:file:///path/to/MyJar.jar!/mypkg/MyClass.class

                     java.lang.Object

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

       The javap command isn't multirelease JAR aware.  Using the class path
       form of the command results in viewing the base entry in all JAR files,
       multirelease or not.  Using the URL form, you can use the URL form of
       an argument to specify a specific version of a class to be
       disassembled.

       The javap command prints its output to stdout.

       Note:

       In tools that support -- style options, the GNU-style options can use
       the equal sign (=) instead of a white space to separate the name of an
       option from its value.

OPTIONS FOR JAVAP
       --help, -help , -h, or -?
              Prints a help message for the javap command.

       -version
              Prints release information.

       -verbose or -v
              Prints additional information about the selected class.

       -l     Prints line and local variable tables.

       -public
              Shows only public classes and members.

       -protected
              Shows only protected and public classes and members.

       -package
              Shows package/protected/public classes and members (default).

       -private or -p
              Shows all classes and members.

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

       -s     Prints internal type signatures.

       -sysinfo
              Shows system information (path, size, date, SHA-256 hash) of the
              class being processed.

       -constants
              Shows static final constants.

       --module module or -m module
              Specifies the module containing classes to be disassembled.

       --module-path path
              Specifies where to find application modules.

       --system jdk
              Specifies where to find system modules.

       --class-path path, -classpath path, or -cp path
              Specifies the path that the javap command uses to find user
              class files.  It overrides the default or the CLASSPATH
              environment variable when it's set.

       -bootclasspath path
              Overrides the location of bootstrap class files.

       --multi-release version
              Specifies the version to select in multi-release JAR files.

       -Joption
              Passes the specified option to the JVM.  For example:


                     javap -J-version

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


              See Overview of Java Options in java.

JAVAP EXAMPLE
       Compile the following HelloWorldFrame class:


              import java.awt.Graphics;

              import javax.swing.JFrame;
              import javax.swing.JPanel;

              public class HelloWorldFrame extends JFrame {

                 String message = "Hello World!";

                 public HelloWorldFrame(){
                      setContentPane(new JPanel(){
                          @Override
                          protected void paintComponent(Graphics g) {
                              g.drawString(message, 15, 30);
                          }
                      });
                      setSize(100, 100);
                  }
                  public static void main(String[] args) {
                      HelloWorldFrame frame = new HelloWorldFrame();
                      frame.setVisible(true);

                  }

              }


       The output from the javap HelloWorldFrame.class command yields the
       following:


              Compiled from "HelloWorldFrame.java"
              public class HelloWorldFrame extends javax.swing.JFrame {
                java.lang.String message;
                public HelloWorldFrame();
                public static void main(java.lang.String[]);
              }


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


              Compiled from "HelloWorldFrame.java"
              public class HelloWorldFrame extends javax.swing.JFrame {
                java.lang.String message;

                public HelloWorldFrame();
                  Code:
                     0: aload_0
                     1: invokespecial #1        // Method javax/swing/JFrame."<init>":()V
                     4: aload_0
                     5: ldc           #2        // String Hello World!
                     7: putfield      #3        // Field message:Ljava/lang/String;
                    10: aload_0
                    11: new           #4        // class HelloWorldFrame$1
                    14: dup
                    15: aload_0
                    16: invokespecial #5        // Method HelloWorldFrame$1."<init>":(LHelloWorldFrame;)V
                    19: invokevirtual #6        // Method setContentPane:(Ljava/awt/Container;)V
                    22: aload_0
                    23: bipush        100
                    25: bipush        100
                    27: invokevirtual #7        // Method setSize:(II)V
                    30: return

                public static void main(java.lang.String[]);
                  Code:
                     0: new           #8        // class HelloWorldFrame
                     3: dup
                     4: invokespecial #9        // Method "<init>":()V
                     7: astore_1
                     8: aload_1
                     9: iconst_1
                    10: invokevirtual #10       // Method setVisible:(Z)V
                    13: return
              }


JDK 17                               2021                             JAVAP(1)