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.TH "JAVAP" "1" "2021" "JDK 17" "JDK Commands"
.hy
.SH NAME
.PP
javap \- disassemble one or more class files
.SH SYNOPSIS
.PP
\f[CB]javap\f[R] [\f[I]options\f[R]] \f[I]classes\f[R]...
.TP
.B \f[I]options\f[R]
Specifies the command\-line options.
See \f[B]Options for javap\f[R].
.RS
.RE
.TP
.B \f[I]classes\f[R]
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.
.RS
.PP
Examples:
.RS
.PP
\f[CB]path/to/MyClass.class\f[R]
.RE
.RS
.PP
\f[CB]jar:file:///path/to/MyJar.jar!/mypkg/MyClass.class\f[R]
.RE
.RS
.PP
\f[CB]java.lang.Object\f[R]
.RE
.RE
.SH DESCRIPTION
.PP
The \f[CB]javap\f[R] command disassembles one or more class files.
The output depends on the options used.
When no options are used, the \f[CB]javap\f[R] command prints the
protected and public fields, and methods of the classes passed to it.
.PP
The \f[CB]javap\f[R] command isn\[aq]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.
.PP
The \f[CB]javap\f[R] command prints its output to \f[CB]stdout\f[R].
.PP
\f[B]Note:\f[R]
.PP
In tools that support \f[CB]\-\-\f[R] style options, the GNU\-style
options can use the equal sign (\f[CB]=\f[R]) instead of a white space to
separate the name of an option from its value.
.SH OPTIONS FOR JAVAP
.TP
.B \f[CB]\-\-help\f[R], \f[CB]\-help\f[R] , \f[CB]\-h\f[R], or \f[CB]\-?\f[R]
Prints a help message for the \f[CB]javap\f[R] command.
.RS
.RE
.TP
.B \f[CB]\-version\f[R]
Prints release information.
.RS
.RE
.TP
.B \f[CB]\-verbose\f[R] or \f[CB]\-v\f[R]
Prints additional information about the selected class.
.RS
.RE
.TP
.B \f[CB]\-l\f[R]
Prints line and local variable tables.
.RS
.RE
.TP
.B \f[CB]\-public\f[R]
Shows only public classes and members.
.RS
.RE
.TP
.B \f[CB]\-protected\f[R]
Shows only protected and public classes and members.
.RS
.RE
.TP
.B \f[CB]\-package\f[R]
Shows package/protected/public classes and members (default).
.RS
.RE
.TP
.B \f[CB]\-private\f[R] or \f[CB]\-p\f[R]
Shows all classes and members.
.RS
.RE
.TP
.B \f[CB]\-c\f[R]
Prints disassembled code, for example, the instructions that comprise
the Java bytecodes, for each of the methods in the class.
.RS
.RE
.TP
.B \f[CB]\-s\f[R]
Prints internal type signatures.
.RS
.RE
.TP
.B \f[CB]\-sysinfo\f[R]
Shows system information (path, size, date, SHA\-256 hash) of the class
being processed.
.RS
.RE
.TP
.B \f[CB]\-constants\f[R]
Shows \f[CB]static\ final\f[R] constants.
.RS
.RE
.TP
.B \f[CB]\-\-module\f[R] \f[I]module\f[R] or \f[CB]\-m\f[R] \f[I]module\f[R]
Specifies the module containing classes to be disassembled.
.RS
.RE
.TP
.B \f[CB]\-\-module\-path\f[R] \f[I]path\f[R]
Specifies where to find application modules.
.RS
.RE
.TP
.B \f[CB]\-\-system\f[R] \f[I]jdk\f[R]
Specifies where to find system modules.
.RS
.RE
.TP
.B \f[CB]\-\-class\-path\f[R] \f[I]path\f[R], \f[CB]\-classpath\f[R] \f[I]path\f[R], or \f[CB]\-cp\f[R] \f[I]path\f[R]
Specifies the path that the \f[CB]javap\f[R] command uses to find user
class files.
It overrides the default or the \f[CB]CLASSPATH\f[R] environment variable
when it\[aq]s set.
.RS
.RE
.TP
.B \f[CB]\-bootclasspath\f[R] \f[I]path\f[R]
Overrides the location of bootstrap class files.
.RS
.RE
.TP
.B \f[CB]\-\-multi\-release\f[R] \f[I]version\f[R]
Specifies the version to select in multi\-release JAR files.
.RS
.RE
.TP
.B \f[CB]\-J\f[R]\f[I]option\f[R]
Passes the specified option to the JVM.
For example:
.RS
.IP
.nf
\f[CB]
javap\ \-J\-version

javap\ \-J\-Djava.security.manager\ \-J\-Djava.security.policy=MyPolicy\ MyClassName
\f[R]
.fi
.PP
See \f[I]Overview of Java Options\f[R] in \f[B]java\f[R].
.RE
.SH JAVAP EXAMPLE
.PP
Compile the following \f[CB]HelloWorldFrame\f[R] class:
.IP
.nf
\f[CB]
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);

\ \ \ \ }

}
\f[R]
.fi
.PP
The output from the \f[CB]javap\ HelloWorldFrame.class\f[R] command yields
the following:
.IP
.nf
\f[CB]
Compiled\ from\ "HelloWorldFrame.java"
public\ class\ HelloWorldFrame\ extends\ javax.swing.JFrame\ {
\ \ java.lang.String\ message;
\ \ public\ HelloWorldFrame();
\ \ public\ static\ void\ main(java.lang.String[]);
}
\f[R]
.fi
.PP
The output from the \f[CB]javap\ \-c\ HelloWorldFrame.class\f[R] command
yields the following:
.IP
.nf
\f[CB]
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
}
\f[R]
.fi