question: public static int intersectionSize ( long [ ] x , long [ ] y ) { final int lx = x . length , ly = y . length ; final int min = ( lx < ly ) ? lx : ly ; int res = 0 ; for ( int i = 0 ; i < min ; i ++ ) { res += Long . bitCount ( x [ i ] & y [ i ] ) ; } return res ; }
target:  Compute the intersection size of two Bitsets.