question: @ Override public int hashCode ( ) { int result = 0 ; Iterator < ? > it = iterator ( ) ; while ( it . hasNext ( ) ) { Object next = it . next ( ) ; result += next == null ? 0 : next . hashCode ( ) ; } return result ; }
target:  Returns the hash code for this set. Two set which are equal must return the same value. This implementation calculates the hash code by adding each element's hash code.