compute a hash code using the hash codes of the underlying objects concode_field_sep F first concode_elem_sep S second concode_field_sep boolean objectsEqual concode_elem_sep boolean equals concode_elem_sep Pair<A,B> create
int function ( ) { return ( first == null ? 0 : first . hashCode ( ) ) ^ ( second == null ? 0 : second . hashCode ( ) ) ; }