JAVA获取两个List的交集、差集以及并集

    public static void main(String[] args) {
        List<String> nameList = new ArrayList<>();
        nameList.add("小明");
        nameList.add("小红");
        nameList.add("小刚");

        List<String> nameList2 = new ArrayList<>();
        nameList2.add("小华");
        nameList2.add("小丽");
        nameList2.add("小刚");

        // 交集
//        nameList.removeIf(e -> !nameList2.contains(e));
//        List<String> finalNameList = nameList;
//        nameList2.removeIf(e -> !finalNameList.contains(e));
//        nameList.addAll(nameList2);
//        // 去重
//        nameList = nameList.stream().distinct().collect(Collectors.toList());
//        System.out.println(nameList);


        // 差集
//        List<String> strings = new ArrayList<>(nameList);
//        nameList.removeIf(e -> nameList2.contains(e));
//        nameList2.removeIf(e -> strings.contains(e));
//        nameList.addAll(nameList2);
//        System.out.println(nameList);
        
        // 并集
        nameList.addAll(nameList2);
        System.out.println(nameList);
    }