question: public static int hashCode ( byte [ ] [ ] field ) { int result = 0 ; for ( int i = 0 , size = field == null ? 0 : field . length ; i < size ; i ++ ) { byte [ ] element = field [ i ] ; if ( element != null ) { result = 31 * result + Arrays . hashCode ( element ) ; } } return result ; }
target:  Computes the hash code of a repeated bytes field. Only the sequence of all non-null elements are used in the computation. Null-value fields and fields of any length with only null elements have the same hash code.