Because I have no recent Backup of the big java project I was working I have to decompile the class Files that are in this jar.
I found 3 different java decompilers for mac os x.

  1. MacJAD (google for Download)
    - onyl able to open single class files
  2. JarInspector (http://www.codeland.org/)
    + can open jar files
    + correct 
    - unable to decompile the anonymous inner classes I use
    - seems to be confused by nested catch and try blocks 
  3. JD-GUI (http://java.decompiler.free.fr/)  
    + can open jar files
    + 90% able to decompiling anonymous inner classes

A big problem all tools share is that if you have nested iterations, for/while loops they all rename the variable you iterate over to 'i$'. So it's possible if your code looks like this:

while(iterator.hashNext()) {
...
    for(int varA; ....){
        for(int varB; ....){.....}
    }
...
}

the decompiled code will end up looking this:

while(i$.hashNext()) {
...
    for(int i$; ....){
        for(int i$; ....){.....}
    }
...
}

which isn't really funny ...

My conclusion is that JarInspector seems to be the best but if you need the inner class support use JD-GUI for the parts of the code those are in.