Decompile Java Applet

/. Online Java Compiler. Code, Compile, Run and Debug java program online. Write your code in this editor and press 'Run' button to execute it. JCavaj Java Decompiler is a free and useful Java-based Java Decompiler You can decompile java applets, jar and zip files producing accurate java source code. JCavaj runs on any platform with Java. JDec - Java Decompiler Online Click to select a file, or drag and drop it here (.class or.jar).

Decompile Java Class File Online
Decompile Java Appleton
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Java Class File Decompiler

Greenhorn

posted 9 years ago

hi everybody
can .class file decompiled into .java file and then after important modification and then after compilation be used as original?
thanks

Bartender

posted 9 years ago

Firstly am not sure if the decompiled version will be exactly same as that of the original file. Moreover, if you have a valid java file with all imports resolved, you can as well edit that file and compile it again. And for decompiling details- you can search in the Beginner or Java General forums.
This is somewhat not encouraged because you would be making use of some else's work. If the code is open sourced then you can download the source directly and this is fine because the original author wanted it to be shared and reused.

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Greenhorn

posted 9 years ago

thanks
may i know what are free decompiler available.
is there decompiler plugine available there?

Ranch Hand

posted 9 years ago

Ranch Hand

posted 9 years ago

Greenhorn

posted 9 years ago

thanks
is decompile code(.class->.java) 100% reliable as original one

Ranch Hand

posted 9 years ago

AFAIK there's no guaranty for a 100% success. I wouldn't rely on it.

Greenhorn

posted 9 years ago

Mehmet Gunacti wrote:AFAIK there's no guaranty for a 100% success. I wouldn't rely on it.

sir thanks
i have a .class file.
original source file missed.
i have to change url in this file
how one can do it?
please tell me sir a successfull way

Ranch Hand

posted 9 years ago

well, create an empty project in your favorite IDE and put the original jar file into the build-path.
decompile the class, put the .java file into your source folder (preserve package structure).
after compilation just update the original jar file using Winrar, drag and drop the new class file and overwrite the original one.
That should do the trick ;)

Bartender

posted 9 years ago

There is no reliable way to do this. Your decompiled java classes may well.. not compile because the decompilation process is not fool proof.
You can however follow the approach mentioned by Mehmet. It will bring you closest to success.
Why are you decompiling anyway ? Did you lose the source ?

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Bartender

posted 9 years ago

It might be a good idea to carefully read the license. Some licenses explicitly forbid decompiling.

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Ranch Hand

posted 9 years ago

Why don't you just use Eclipse IDE to open .class file? Eclipse has everything you need for the project..harness the tool to it full power.

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Ranch Hand

posted 9 years ago

well mr pandy may be completely innocent, but i always thought one of the big advantages of compilers vs interpreters is that your source code is sate.

Sheriff

posted 9 years ago

Safe? No. You can do your best to make it hard to decompile, by using a code obfuscator, but in the end most of the code can be decompiled. After all, the JVM needs to be able to read the byte code, and therefore so can any decompiler.

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Ranch Hand

posted 9 years ago

the question is, why did the designers of Java allow that ?
they must have discussed this, and accepted the fact that Java code will be decompilable.
Shouldn't they have included an option (parameter maybe ?) that would prevent decompilation ?

Bartender

posted 9 years ago

Mehmet Gunacti wrote:the question is, why did the designers of Java allow that ?
they must have discussed this, and accepted the fact that Java code will be decompilable.
Shouldn't they have included an option (parameter maybe ?) that would prevent decompilation ?

The JLS and the class format are specifications. This means your specification can have a JVM vendor (Sun/IBM/JBOSS) and it allows for freedom. You need not be tied down with a vendor.

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Marshal

Decompile Java Class File Online

posted 9 years ago

Design your own monogram free. Mehmet Gunacti wrote:. . . an option (parameter maybe ?) that would prevent decompilation ?

As Rob has already told us, if you can execute the bytecode you can decompile it. So it is not possible to prevent decompilation.

Ranch Hand

posted 9 years ago

Campbell Ritchie wrote:

Mehmet Gunacti wrote:. . . an option (parameter maybe ?) that would prevent decompilation ?

As Rob has already told us, if you can execute the bytecode you can decompile it. So it is not possible to prevent decompilation.
You mean, if you can interpret the code, you can decompile it.
Still, there should be a mechanism like, compiling the java source code to binary instead of bytecode. the JVM should then be able to run binary-bytecode..
ok, I was just thinking loud.
AFAIK one is able to decompile .net code (intermediate language ?), too, right ? So I guess MS would have prevented that, if there would be a way to do it.

Bartender

posted 9 years ago

run binary-bytecode..

Assembly you mean ? Here are some links that can clarify the matter for you

Decompile Java Appleton

http://en.wikipedia.org/wiki/Bytecode
http://en.wikipedia.org/wiki/Assembly_language
http://en.wikipedia.org/wiki/Just-in-time_compilation

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Ranch Hand

posted 9 years ago

Deepak Bala wrote:

run binary-bytecode..

Assembly you mean ? Here are some links that can clarify the matter for you

Was just wondering why they didn't come up with a method to prevent decompiling Java classes.
It's not possible, I guess, that's why.
Yes, I meant assembly (or machine code). sorry for the inappropriate term.
Thanks for the links.

Decompile Java Exe

Marshal

posted 9 years ago

Compiling to machine code would tie your application to a particular platform. You would have to recompile a Windows® application to run on a Mac, for example.

Greenhorn

posted 9 years ago

Java Class File Decompiler

I haven't had cause to look into it, but there are Java Obfuscators that will attempt to amend your class files to prevent/make decompilation difficult. If that's something that concerns you.