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JAD is one of the best Java Decompiler today. This is one brilliant piece of software. Nevertheless, the last JDK supported by JAD 1.5.8 (Apr 14, 2001) is JDK 1.3.
DJ Java Decompiler, JadClipse, Cavaj and JarInspector are powered by Jad. The last version of Decafe Pro has been released on 2002-01-03.
These viewers can not display Java 5 sources.
So, I use JD-GUI : logic, I'm the author :)
Procyon is a new open source decompiler that already beats JD-GUI in most cases. It's written in Java and comes in a self-contained jar. It is actively developed by StackOverflow's own Mike Strobel.
Update February 2016:
www.javadecompilers.com lists JAD as being:
the most popular Java decompiler, but primarily of this age only. Written in C++, so very fast.
Outdated, unsupported and does not decompile correctly Java 5 and later
So your mileage may vary with recent jdk (7, 8).
The same site list other tools.
And javadecompiler, as noted by Salvador Valencia in the comments (Sept 2017), offers a SaaS where you upload the .class file to the cloud and it returns you the decompiled code.
Original answer: Oct. 2008
- The final release of JSR 176, defining the major features of J2SE 5.0 (Java SE 5), has been published on September 30, 2004.
- The lastest Java version supported by JAD, the famous Java decompiler written by Mr. Pavel Kouznetsov, is JDK 1.3.
- Most of the Java decompilers downloadable today from the Internet, such as โDJ Java Decompilerโ or โCavaj Java Decompilerโ, are powered by JAD: they can not display Java 5 sources.
Java Decompiler (Yet another Fast Java decompiler) has:
- Explicit support for decompiling and analyzing Java 5+ โ.classโ files.
- A nice GUI:
It works with compilers from JDK 1.1.8 up to JDK 1.7.0, and others (Jikes, JRockit, etc.).
It features an online live demo version that is actually fully functional! You can just drop a jar file on the page and see the decompiled source code without installing anything.
There are a few decompilers out there... A quick search yields:
- Procyon: open-source (Apache 2) and actively developed
- Krakatau: open-source (GPLv3) and actively developed
- CFR: open-source (MIT) and actively developed
- JAD
- DJ Java Decompiler
- Mocha
And many more.
These produce Java code. Java comes with something that lets you see JVM byte code (javap).