1.你可以新建一个list

        List<Integer> list=new ArrayList<>();
        int i=0;
        while (i<100){
            list.add(i++);
        }

        List<Integer> subList = list.subList(list.size()-1, list.size());
        System.out.println("原list大小--"+list.size());
        System.out.println("新list大小--"+subList.size());
        System.out.println("原list最后的数字--"+list.get(list.size()-1));
        System.out.println("新list的第一个数字--"+subList.get(0));

2.你确实不想新建一个要在原list做修改

 		List<Integer> list=new ArrayList<>();
        int i=0;
        while (i<100){
            list.add(i++);
        }
  		System.out.println("原list大小--"+list.size());
        System.out.println("原list最后的数字--"+list.get(list.size()-1));
        list.subList(0, list.size()-1).clear();
        System.out.println("新list大小--"+list.size());
        System.out.println("新list最后的数字--"+list.get(0));