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The language it produces is still bytecode (not anything like Java), but it's fairly readable and extremely instructive. Also, if you really want to, you can open up any . class file in a hex editor and read the bytecode directly. The result is identical to using javap .
A simple way to see what String literals are used in a ". class" file is to use the javap utility in your JDK installation to dump the file using the "-v" option. Then grep for text that looks like <String "..."> where ... is the String you are looking for.
class without source default to Class Decompiler Viewer . Now, click on the class or methods, press F3 , and the plugin will automatically decompile the Java class.
jd-gui is the best decompiler at the moment. it can handle newer features in Java, as compared to the getting-dusty JAD.
If you don't mind reading bytecode, javap should work fine. It's part of the standard JDK installation.
Usage: javap <options> <classes>...
where options include:
-c Disassemble the code
-classpath <pathlist> Specify where to find user class files
-extdirs <dirs> Override location of installed extensions
-help Print this usage message
-J<flag> Pass <flag> directly to the runtime system
-l Print line number and local variable tables
-public Show only public classes and members
-protected Show protected/public classes and members
-package Show package/protected/public classes
and members (default)
-private Show all classes and members
-s Print internal type signatures
-bootclasspath <pathlist> Override location of class files loaded
by the bootstrap class loader
-verbose Print stack size, number of locals and args for methods
If verifying, print reasons for failure
As pointed out by @MichaelMyers, use
javap -c <name of java class file>
to get the JVM assembly code. You may also redirect the output to a text file for better visibility.
javap -c <name of java class file> > decompiled.txt
You want a java decompiler, you can use the command line tool javap to do this. Also, Java Decompiler HOW-TO describes how you can decompile a class file.
what you are looking for is a java de-compiler. I recommend JAD http://www.kpdus.com/jad.html It's free for non commercial use and gets the job done.
Note: this isn't going to make the code exactly the same as what was written. i.e. you're going to lose comments and possibly variable names, so it's going to be a little bit harder than just reading normal source code. If the developer is really secretive they will have obfuscated their code as well, making it even harder to read.
cpuguru, if your applet has been compiled with javac 1.3 (or less), your best option is to use Jad.
Unfortunately, the last JDK supported by JAD 1.5.8 (Apr 14, 2001) is JDK 1.3.
If your applet has been compiled with a more recent compiler, you could try JD-GUI : this decompiler is under development, nevertheless, it generates correct Java sources, most of time, for classes compiled with the JDKs 1.4, 1.5 or 1.6.
DarenW, thank you for your post. JD-GUI is not the best decompiler yet ... but I'm working on :)
jd-gui "http://code.google.com/p/innlab/downloads/detail?name=jd-gui-0.3.3.windows.zip&can=2&q=" is the best and user friendly option for decompiling .class file....
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