// onjava/Sets.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
package onjava;
import java.util.*;

public class Sets {
 public static <T> Set<T> union(Set<T> a, Set<T> b) {
 Set<T> result = new HashSet<>(a);
 result.addAll(b);
 return result;
 }
 public static <T>
 Set<T> intersection(Set<T> a, Set<T> b) {
 Set<T> result = new HashSet<>(a);
 result.retainAll(b);
 return result;
 }
 // Subtract subset from superset:
 public static <T> Set<T>
 difference(Set<T> superset, Set<T> subset) {
 Set<T> result = new HashSet<>(superset);
 result.removeAll(subset);
 return result;
 }
 // Reflexive--everything not in the intersection:
 public static
 <T> Set<T> complement(Set<T> a, Set<T> b) {
 return difference(union(a, b), intersection(a, b));
 }
}