From 24afdffe2ce31b698ff6a27f44811eae2777413e Mon Sep 17 00:00:00 2001 From: tianyu94 Date: Wed, 3 Jul 2019 09:44:22 +0800 Subject: [PATCH] =?UTF-8?q?=E4=BF=AE=E5=A4=8D=E6=8B=BC=E5=86=99=E9=94=99?= =?UTF-8?q?=E8=AF=AF?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- docs/java/collection/Java集合框架常见面试题.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/docs/java/collection/Java集合框架常见面试题.md b/docs/java/collection/Java集合框架常见面试题.md index 0e5d4103..13a4fa00 100644 --- a/docs/java/collection/Java集合框架常见面试题.md +++ b/docs/java/collection/Java集合框架常见面试题.md @@ -284,7 +284,7 @@ static class Segment extends ReentrantLock implements Serializable { ### JDK1.8 （上面有示意图） -ConcurrentHashMap取消了Segment分段锁，采用CAS和synchronized来保证并发安全。数据结构跟HashMap1.8的结构类似，数组+链表/红黑二叉树。Java 8在链表长度超过一定阈值（8）时将链表（寻址时间复杂度为O(N)）转换为红黑树（寻址时间复杂度为O(long(N))） +ConcurrentHashMap取消了Segment分段锁，采用CAS和synchronized来保证并发安全。数据结构跟HashMap1.8的结构类似，数组+链表/红黑二叉树。Java 8在链表长度超过一定阈值（8）时将链表（寻址时间复杂度为O(N)）转换为红黑树（寻址时间复杂度为O(log(N))） synchronized只锁定当前链表或红黑二叉树的首节点，这样只要hash不冲突，就不会产生并发，效率又提升N倍。