question: public Pair < Integer , List < Long > > next ( ) { try { classesProcessed ++ ; Integer key = iterator . next ( ) ; long pos = classificationBlockRMA2 . getPos ( key ) ; int count = classificationBlockRMA2 . getSum ( key ) ; classDumpReader . seek ( pos ) ; List < Long > list = new LinkedList < > ( ) ; for ( int i = 0 ; i < count ; i ++ ) list . add ( classDumpReader . readLong ( ) ) ; return new Pair < > ( key , list ) ; } catch ( Exception e ) { Basic . caught ( e ) ; error = true ; return null ; } }
target:  Returns the next element in the iteration.