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Snailclimb merged 1 commit into from
Jul 13, 2023
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Update hashmap-source-code.md #2078

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6 changes: 1 addition & 5 deletions docs/java/collection/hashmap-source-code.md
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Expand Up @@ -262,12 +262,8 @@ HashMap 只提供了 put 用于添加元素，putVal 方法只是给 put 方法
1. 如果定位到的数组位置没有元素 就直接插入。
2. 如果定位到的数组位置有元素就和要插入的 key 比较，如果 key 相同就直接覆盖，如果 key 不相同，就判断 p 是否是一个树节点，如果是就调用`e = ((TreeNode<K,V>)p).putTreeVal(this, tab, hash, key, value)`将元素添加进入。如果不是就遍历链表插入(插入的是链表尾部)。

![ ](https://my-blog-to-use.oss-cn-beijing.aliyuncs.com/2019-7/put方法.png)
![ ](https://qingcheng-davin.oss-cn-shenzhen.aliyuncs.com/put.png)

说明:上图有两个小问题：

- 直接覆盖之后应该就会 return，不会有后续操作。参考 JDK8 HashMap.java 658 行（[issue#608](https://github.com/Snailclimb/JavaGuide/issues/608)）。
- 当链表长度大于阈值（默认为 8）并且 HashMap 数组长度超过 64 的时候才会执行链表转红黑树的操作，否则就只是对数组扩容。参考 HashMap 的 `treeifyBin()` 方法（[issue#1087](https://github.com/Snailclimb/JavaGuide/issues/1087)）。

```java
public V put(K key, V value) {
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