You must get an Exception java.lang.classNotFoundException:classA now and you try to find out why&how.
You get java.lang.classNotFoundException because the java class-loader can’t find classA in class path, so the very thing you shoud do is checking your Class Path. mostly, this will cover 90% situations.
YOU CAN PASTE YOUR EXCEPTION DETAILS IN REPLY, AND I”LL TRY TO HELP.