Accenture interview question

difference between wait() and sleep(). difference between aggregation, association, composition. final, finally, finalize. QueryDSL in hibernate Typesafe queries Dirtycheck in hibernate @inject and @ autowired differnce. why concurrent hashmap can't contain null key and values. why wait, notify and notifyAll are called from object class? program to find the no. of occurrences of elements in an array.