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pull merged 2 commits into from
May 24, 2021
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[pull] master from Snailclimb:master #137

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Update ConcurrentHashMap源码+底层数据结构分析.md
tangj1992 May 24, 2021
7f29c42
Merge pull request #1205 from tangj1992/patch-1
Snailclimb May 24, 2021
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2 changes: 1 addition & 1 deletion docs/java/collection/ConcurrentHashMap源码+底层数据结构分析.md
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Expand Up @@ -91,7 +91,7 @@ public ConcurrentHashMap(int initialCapacity,float loadFactor, int concurrencyLe
总结一下在 Java 7 中 ConcurrnetHashMap 的初始化逻辑。

1. 必要参数校验。
2. 校验并发级别 concurrencyLevel 大小，如果大于最大值，重置为最大值。无惨构造**默认值是 16.**
2. 校验并发级别 concurrencyLevel 大小，如果大于最大值，重置为最大值。无参构造**默认值是 16.**
3. 寻找并发级别 concurrencyLevel 之上最近的 **2 的幂次方**值，作为初始化容量大小，**默认是 16**。
4. 记录 segmentShift 偏移量，这个值为【容量 = 2 的N次方】中的 N，在后面 Put 时计算位置时会用到。**默认是 32 - sshift = 28**.
5. 记录 segmentMask，默认是 ssize - 1 = 16 -1 = 15.
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