CollectionUtils取交集,并集和差集

import org.apache.commons.collections.CollectionUtils;

 <dependency>
      <groupId>commons-collections</groupId>
      <artifactId>commons-collections</artifactId>
      <version>${commons-collections.version}</version>
    </dependency>

public static void main(String[] args) {

        List<String> listA = new ArrayList<String>();
        listA.add("a");
        listA.add("b");
        listA.add("b");
        listA.add("c");
        List<String> listB = new ArrayList<String>();
        listB.add("a");
        listB.add("e");
        listB.add("f");
        System.out.println("集合A:"+listA);
        System.out.println("集合B:"+listB);
        System.out.println("------------------------");
        //并集
        Collection<String> union = CollectionUtils.union(listA, listB);
        System.out.println("并集："+union);
        //交集
        Collection<String> intersection = CollectionUtils.intersection(listA, listB);
        System.out.println("交集："+intersection);
        //交集的补集
        Collection<String> disjunction = CollectionUtils.disjunction(listA, listB);
        System.out.println("交集的补集   ："+disjunction);
        //差集(集合相减)
        Collection<String> subtract = CollectionUtils.subtract(listA, listB);
        System.out.println("差集(集合相减)   ："+subtract);
    }

集合A:[a, b, b, c]
集合B:[a, e, f]
------------------------
并集：[a, b, b, c, e, f]
交集：[a]
交集的补集   ：[b, b, c, e, f]
差集(集合相减)   ：[b, b, c]