question: public static long pop_xor ( long [ ] arr1 , long [ ] arr2 , int wordOffset , int numWords ) { long popCount = 0 ; for ( int i = wordOffset , end = wordOffset + numWords ; i < end ; ++ i ) { popCount += Long . bitCount ( arr1 [ i ] ^ arr2 [ i ] ) ; } return popCount ; }
target:  Returns the popcount or cardinality of A ^ B Neither array is modified. 