测试类
抱歉第三题使用了TreeSet，做到第四题发现实现不了因为TreeSet没有索引，所以第四题还是用了ArrayList

package com.imooc.chapter14test;

import java.util.*;

public class MovieSetTest {
    public static void main(String[] args) {
        //定义电影Set集合
        List<MovieDB> movieList = new ArrayList<>();
        MovieDB movie1 = new MovieDB("肖申克的救赎","1994",9.7f);
        MovieDB movie2 = new MovieDB("阿甘正传","1994",9.5f);
        MovieDB movie3 = new MovieDB("千与千寻","2001",9.4f);
        MovieDB movie4 = new MovieDB("星际穿越","2014",9.4f);
        MovieDB movie5 = new MovieDB("楚门的世界","1998",9.4f);
        MovieDB movie6 = new MovieDB("放牛班的春天","2004",9.3f);
        MovieDB movie7 = new MovieDB("当幸福来敲门","2006",9.2f);
        movieList.add(movie1);
        movieList.add(movie2);
        movieList.add(movie3);
        movieList.add(movie4);
        movieList.add(movie5);
        movieList.add(movie6);
        movieList.add(movie7);
        //在第二个元素位置添加电影信息
        movieList.add(1, new MovieDB("霸王别姬", "1993",9.6f));
        //删除集合的最后一个元素
        //取得集合的元素个数-1便是最后一个元素的索引下标
        movieList.remove(movieList.size()-1);
        //将电影《楚门的世界》的评分改成 9.5 分
        //遍历元素，如果发现元素的电影名称等于楚门的世界，就通过set方法修改豆瓣评分
        for (MovieDB item:
             movieList) {
            if(item.getName().equals("楚门的世界")){
                item.setDoubanScore(9.5f);
            }
        }
		//遍历集合元素并打印
        for (MovieDB item:
             movieList) {
            System.out.println("电影名称: " + item.getName() + ",上映年份: " + item.getReleaseDate() + ",豆瓣评分: "+item.getDoubanScore());
        }
    }
}