Lambda表达式获取差集、交集、并集

使用Lambda进行获取两个集合之间的差集、交集、并集

   @Test
    public void doSome(){
        List oldList = Arrays.asList("1", "2", "3", "4");
        List newList = Arrays.asList("3", "4", "5", "6");

        getDiffSet(oldList, newList);
        getDiffSet(newList, oldList);
        getIntersection(oldList, newList);
        getUnion(oldList, newList);
    }

    //差集方法
    private void getDiffSet(List oldList, List newList) {
        List collect = newList.stream().filter(str -> {
            return !oldList.contains(str);
        }).collect(toList());
        log.info("差集内容--{}", JSON.toJSONString(collect));
    }

    //交集方法
    private void getIntersection(List oldList, List newList) {
        List collect = newList.stream().filter(str -> {
            return oldList.contains(str);
        }).collect(toList());
        log.info("交集内容--{}", JSON.toJSONString(collect));
    }

    //并集
    private void getUnion(List oldList, List newList) {
        //使用新的集合 不然会报错
        List collectOld = oldList.parallelStream().collect(toList());
        List collectNew = newList.parallelStream().collect(toList());
        //并集
        collectOld.addAll(collectNew);
        List collect = collectOld.stream().distinct().collect(toList());
        log.info("并集内容--{}", JSON.toJSONString(collect));
    }

结果集：

差集内容--["5","6"]
差集内容--["1","2"]
交集内容--["3","4"]
并集内容--["1","2","3","4","5","6"]