1、maven包依赖

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-collections4</artifactId>
    <version>4.1</version>
</dependency>

2、具体代码

public class demo {

    //两个集合也可以是对象集合
    public static void main(String[] args) {
        List<String> list1 = new ArrayList<String>();
        List<String> list2 = new ArrayList<String>();

        String String1 = new String("1");
        String String2 = new String("2");
        String String3 = new String("1");
        String String4 = new String("4");

        list1.add(String1);
        list1.add(String2);

        list2.add(String3);
        list2.add(String4);

        List<String> union = getUnion(list1,list2);
        System.out.println("并集："+union);

        List<String> intersection = getIntersection(list1,list2);
        System.out.println("交集："+intersection);

        List<String> disjunction = getDisjunction(list1,list2);
        System.out.println("交集的补集："+disjunction);

        List<String> subtract = getSubtract(union,list1);
        System.out.println("差集："+subtract);
    }

    //获取两个集合并集（自动去重）
    public static List<String> getUnion(List<String> list1, List<String> list2){
        List<String> union = (List<String>) CollectionUtils.union(list1, list2);
        return union;
    }

    //获取两个集合交集
    public static List<String> getIntersection(List<String> list1,List<String> list2){
        List<String> intersection = (List<String>)CollectionUtils.intersection(list1, list2);
        return intersection;
    }
    //获取两个集合交集的补集 即 list1 + list2 - 交集
    public static List<String> getDisjunction(List<String> list1,List<String> list2){
        List<String> disjunction = (List<String>)CollectionUtils.disjunction(list1, list2);
        return disjunction;
    }

    //获取两个集合的差集 list1 - 交集
    public static List<String> getSubtract(List<String> list1,List<String> list2){
        List<String> subtract = (List<String>)CollectionUtils.subtract(list1, list2);
        return subtract;
    }

}

运行结果：