override - Listening for when a method is called in a class, and then possibly overriding it (java) -

so, let's have 2 classes, foo1 , foo2, in separate library.

foo2 class instantiated, , cannot correctly reinstintate subclass override method in foo2.

is there way can listen method called in foo2, , possibly cancel execution of said method, , there create method. understand if i"m saying confusing, can :).

    class foo{      void x(){     if (foo2.x2().called){     //do stuff     }     }     }      class foo2{     void x2(){     //stuff done here...     }     } 

obviously, above code won't anything, simple example of looking for.

if can't somehow subclass foo2 or modify existing lib (in worst case decompile/modify/recompile) use aspectj intercept calls.

you'd want use load-time weaving purpose. check out general documentation load-time weaving here: http://www.eclipse.org/aspectj/doc/next/devguide/ltw.html. it's involved procedure add/configure aspectj though i'd recommend last resort