By doing this you will get something highly similar to CL's conditions. In CL, there is mechanism similar to Java exceptions (throw/catch/unwind-protect) that is - among other things - used by condition system to actually unwind stack when it determines that is necessary. So you can probably abuse Java exceptions to implement condition system or - more generally - escape continuations.

Problem is that such mechanism has to be used consistently everywhere to be useful. And when you find yourself rewriting standard library, you could well use CL instead of Java.