List集合使用 Collections.sort 排序

public static void main(String[] args) {
        List<Integer> sortList = new ArrayList<>();
        sortList.add(3);
        sortList.add(9);
        sortList.add(6);
        sortList.add(1);
        for (Integer num: sortList) {
            System.out.print(num+" ");
        }
        Collections.sort(sortList, new Comparator<Integer>() {
            @Override
            //o1-o2 从小到大 ，o2-o1 从大到小
            public int compare(Integer o1, Integer o2) {
                return o2-o1;
            }
        });
        System.out.println("--------");
        for (Integer num: sortList) {
            System.out.print(num+" ");
        }

    }