如果您知道,请描述原因.我用谷歌搜索了它,但没有找到解释清楚的答案.
Please describe the reason if you know. I Googled it, but didn't find well explained answers.
当您的 hashCode
为负数时,是否使存储桶的索引为正数?
Is it for making index of bucket positive when your hashCode
is negative?
对于HashMap
,存储Map的条目的数组中的索引是这样计算的(其中h
由 key 的 hashCode
计算得出):
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
是数组的长度.
Where length
is the length of the array.
这仅在 length
是 2 的幂时有效.如果 length
不是 2 的幂,则必须将此代码更改为效率较低的 返回 h % 长度
.
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
.
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