The Java compiler compiles Java source code into class files(bytecode) and then the Java interpreter interprets the bytecode. So, the Java bytecode is easy to decompile into source code. Many tools are available to do this task. But I prefer JD Java Decompiler (http://jd.benow.ca), because it is easy to use and it have better user interface.
Also the 'Java Decompiler' plug in available for Eclipse and IntelliJ IDEs.
Linux: http://jd.benow.ca/jd-gui/downloads/jd-gui-0.3.5.linux.i686.tar.gz
Mac: http://jd.benow.ca/jd-gui/downloads/jd-gui-0.3.5.osx.i686.dmg
Also the 'Java Decompiler' plug in available for Eclipse and IntelliJ IDEs.
Download Link:
Windows: http://jd.benow.ca/jd-gui/downloads/jd-gui-0.3.7-RC-1.windows.zipLinux: http://jd.benow.ca/jd-gui/downloads/jd-gui-0.3.5.linux.i686.tar.gz
Mac: http://jd.benow.ca/jd-gui/downloads/jd-gui-0.3.5.osx.i686.dmg
