The contract for java.util.Iterator specifies that next() should throw a NoSuchElementException "if the iteration has no more elements". Instead, the java driver throws a RuntimeException. See http://docs.oracle.com/javase/7/docs/api/java/util/Iterator.html#next() for more details.

Backwards compatibility: IMO, this can be fixed without backwards compatibility concerns, because NoSuchElementException is a subclass of RuntimeException.