求两个list的交集和并集

    static void getIntersection() {
        List<Long> r1 = new ArrayList<>();
        r1.add(1L);
        r1.add(2L);
        r1.add(3L);
        r1.add(4L);
        r1.add(5L);
        System.out.println("M" + r1);
        List<Long> r2 = new ArrayList<>();
        r2.add(11L);
        r2.add(12L);
        r2.add(13L);
        r2.add(4L);
        r2.add(5L);
        Set<Long> hashSet = new HashSet<>(r1);
        System.out.println("N" + r2);

        List<Long> r3 = new ArrayList<>();
        int count = hashSet.size();
        for (int i = 0; i < r2.size(); i++) {
            hashSet.add(r2.get(i));
            if (hashSet.size() == count) {
                r3.add(r2.get(i));
            } else {
                count++;
            }
        }
        System.out.println("交集" + r3);
    }