4. 创建一个List集合的对象，添加几条数据，将1号位和2号位交换；获得最大值，最小值打印出来，最后再遍历该集合并把元素打印出来_list.add(0,1)

 public static void main(String[] args) {
        List<Integer> list = new ArrayList<>();
        list.add(0);
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);

        System.out.println("修改前："+list);

        Collections.swap(list,0,1);
        System.out.println("修改后："+list);

        Collections.sort(list);  //排序list
        System.out.println("排序后："+list);

        System.out.println( "最大："+Collections.max(list));
        System.out.println("最小："+Collections.min(list));
        System.out.println("一、--------------");
        for (int i = 0; i < list.size(); i++) {
            System.out.println(list.get(i));
        }
        System.out.println("二、--------------");
        for (Integer i:list){
            System.out.println(i);
        }
        System.out.println("三、--------------");
        Iterator<Integer> it = list.iterator();
        while (it.hasNext()){
            Integer next= it.next();
            System.out.println(next);
        }

    }