import java.util.*;
public class RetainAll {
   public static void main(String[] args) {
     Set s1 = new HashSet();
     Set s2 = new HashSet();
     s1.add("a");s1.add("b");s1.add("c");
     s2.add("d");s2.add("a");s2.add("b");
     Set sn = new HashSet(s1);
     sn.retainAll(s2);
     Set su = new HashSet(s1);
     su.addAll(s2);
     System.out.println(sn);
     System.out.println(su);
   }
}