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 pro-
cessed 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 de-
pends 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 disassem-
bled.
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 environ-
ment 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 fol-
lowing:
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 21 2023 JAVAP(1)
Generated by dwww version 1.15 on Sat Jun 29 02:30:52 CEST 2024.