<dependency>
   <groupId>com.google.guava</groupId>
   <artifactId>guava</artifactId>
   <version>22.0</version>
  </dependency>
  <dependency>
   <groupId>org.apache.commons</groupId>
   <artifactId>commons-collections4</artifactId>
   <version>4.1</version>
  </dependency>

  //交集
  Set<Integer> intersectionSet = Sets.intersection(set1, set2);
  //差集
  Set<Integer> subtractSet = Sets.difference(set1, set2);
  //并集
  Set<Integer> unionSet = Sets.union(set1, set2);

  //交集
  Collection<Integer> intersectionSet = CollectionUtils.intersection(set1, set2);
  //差集
  Collection<Integer> subtractSet = CollectionUtils.subtract(set1, set2);
  //并集
  Collection<Integer> unionSet = CollectionUtils.union(set1, set2);