javap
Disassembles one or more class files.
Synopsis
javap [options] classfile...
classfile
: One or more classes separated by spaces to be processed for annotations such asDocFooter.class
. You can specify a class that can be found in the class path, by its file name or with a URL such asfile:///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 thejavap
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
-s
: Prints internal type signatures.-sysinfo
: Shows system information (path, size, date, MD5 hash) of the class being processed.-constants
: Showsstatic 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 thejavap
command uses to look up classes. Overrides the default or theCLASSPATH
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 injre/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 ofjava.ext.dirs
.
Example
The output from the javap DocFooter.class
command yields the following:
Compiled from "DocFooter.java"
public class t5750.javap.DocFooter extends java.applet.Applet {
java.lang.String date;
java.lang.String email;
public t5750.javap.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 t5750.javap.DocFooter extends java.applet.Applet {
java.lang.String date;
java.lang.String email;
public t5750.javap.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
}