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1、在开发工作中，我们有时需要去判断List集合中是否含有重复的元素
2、我们不需要找出重复的元素，我们只需要返回一个 Boolean 类型就可以了
3、如果使用循环遍历的方式，将会消耗大量的性能
4、我们知道，Set 中存放的都是不重复的数据，所以只需要将 List 集合转化为 Set 集合，再进行比较即可
代码如下：
package com.test; import java.util.ArrayList; import java.util.HashSet; import
java.util.List; public class Test { public static void main(String[] args) { //
定义一个 list 集合 List<String> list = new ArrayList<String>(); // 往 list 里面添加数据 list.
add("a"); list.add("b"); list.add("a"); list.add("c"); // 将 list 转化为 set HashSet
<String> set = new HashSet<>(list); // 比较 list 与 set 的长度 Boolean result = set.
size() == list.size() ? true : false; // 输出比较结果 System.out.println(result); } }
运行结果当然是：false
如您在阅读中发现不足，欢迎留言！！！
