一段代码让你理解set和list的区别

先看代码，最好亲自写

package com.leilei;import java.util.ArrayList;import java.util.Collection;import java.util.HashSet;import java.util.Iterator;import java.util.List;import java.util.Set;public class HashSetTest {public static void main(String[] args) {List lists = new ArrayList();lists.add("1");lists.add("2");lists.add("3");lists.add("2");System.out.println(lists);for(Object object:lists){String list = (String)object;System.out.println(list);}System.out.println("------------------------");// 创建集合添加元素Set books = new HashSet();books.add("1");books.add("2");books.add("3");books.add("3");System.out.println(books);//遍历集合for(Object object:books){String book = (String)object;System.out.println(book);}}}

再看运行结果

----------------------------------------------------这里开始----------------------------------------------------------------

[1, 2, 3, 2]
1
2
3
2
------------------------
[3, 2, 1]
3
2
1

----------------------------------------------------这里结束----------------------------------------------------------------

结论：list存储有序可重复的对象，set存储无序不可重复的set，添加重复数据会失败。