問題描述
如果您知道，請描述原因.我用谷歌搜索了它，但沒有找到解釋清楚的答案.
Please describe the reason if you know. I Googled it, but didn't find well explained answers.
當您的 hashCode 為負數時，是否使存儲桶的索引為正數?
Is it for making index of bucket positive when your hashCode is negative?
推薦答案
對于HashMap，存儲Map的條目的數組中的索引是這樣計算的(其中h 由 key 的 hashCode 計算得出):
For HashMap, the index in the array that stores the entries of the Map is calculated this way (where h is calculated from the hashCode of the key):
static int indexFor(int h, int length) {
return h & (length-1);
}
其中 length 是數組的長度.
Where length is the length of the array.
這僅在 length 是 2 的冪時有效.如果 length 不是 2 的冪，則必須將此代碼更改為效率較低的 返回 h % 長度.
This only works when length is a power of 2. If length wasn't power of 2, you would have to change this code to the less efficient return h % length.
這篇關于為什么HashMap的初始容量是16(2的冪)和Hashtable的初始容量是11(素數)?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！