There's a discussion here that answers your question. http://stackoverflow.com/questions/11130145/hadoop-multipleinputs-fails-with-classcastexception ... View more

Thanks @Rich Raposa. It was actually little confusing to see ONLY setGroupingComparator mentioned in the objective, while secondary-sort involves writing comparator classes for sorting/grouping and using both setSortComparatorClass and setGroupingComparator methods. ... View more

Thank you very much @Rich Raposa. ... View more