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补充一些细节 #1

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4 changes: 2 additions & 2 deletions Java并发容器和框架.md
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#### ConcurrentHashMap

HashMap线程不安全，并行put的时候有可能导致HashMap的Entry链表形成环形数据结构，next永不为空，陷入死循环
HashMap线程不安全，在jdk 1.7时，HashMap使用头插法插入链表，所以每次发生扩容的时候，进行链表复制时，都会翻转链表，所以并行put的并发生扩容的时候有可能导致HashMap的Entry链表形成环形数据结构，next永不为空，陷入死循环

```java
package com.company.concurrentclass.hashmapdeadend;
Expand Down Expand Up @@ -34,7 +34,7 @@ public class DeadEndHashMap {



ConcurrentHashMap使用了分段锁技术，一段数据配一把锁，其它段的数据不受影响。HashMap key value可以为null 但是ConcurrentHashMap不允许，直接会判处异常
ConcurrentHashMap使用了分段锁技术，一段数据配一把锁，其它段的数据不受影响（jdk1.8改为CAS锁，并引入红黑树）。HashMap key value可以为null 但是ConcurrentHashMap不允许，直接会判处异常