@CanIgnoreReturnValue
  static Object checkElementNotNull(Object element, int index) {
    if (element == null) {
      throw new NullPointerException("at index " + index);
    }
    return element;
  }
@CanIgnoreReturnValue
  static Object checkElementNotNull(Object element, int index) {
    if (element == null) {
      throw new NullPointerException("at index " + index);
    }
    return element;
  }
@ CanIgnoreReturnValue static Object checkElementNotNull ( Object element , int index ) { if ( element == null ) { throw new NullPointerException ( "at index " + index ) ; } return element ; }
creation cost.
creation cost .