while browsing, trying to solve a problem, came across classpath, but when i tried it i found a bug in the bit i wanted to use,( URL class ) which appeared easy to fix, wrote what i thought was a fix but now can't seem to find a nice way to run it. i am trying NOT to set up another development environment and really just want to replace the existing class and run it. here's what i've tried so far; used IKVM, but the -xbootclasspath option doesn't override the existing classes. (this seems like a bug which i've posted.). tried to compile classpath using jikes to run under sun JVM but get this; Found 1 semantic error compiling "C:/Program Files/classpath/java/lang/ClassLoader.java": <-------------------------------- 1097. new URLClassLoader(urls, parent) . . . 1112. }; --------> *** Error: A constructor associated with this anonymous type does not throw the exception "java/lang/SecurityException" thrown by its super type, "java/net/URLClassLoader". and i'm only doing that because i can't find a runtime anywhere. ( is this because runtime's are somehow VM dependent, and it's too difficult to maintain a runtime for this VM? ) please help, getting a bit frustrated, a simple bit of hit and run contribution, has turned into a week of annoyance. simon.