public void union(Set x){
  Enumeration elements=x.elements();
  while (elements.hasMoreElements())   put(elements.nextElement());
}

public void union ( Set x ) { Enumeration elements = x . elements ( ) ; while ( elements . hasMoreElements ( ) ) put ( elements . nextElement ( ) ) ; }
destructively modify this so that it becomes the union of itself with x . we iterate over the elements in x , adding to this any that are not in x .
