static int hash(int h) {
// This function ensures that hashCodes that differ only by
// constant multiples at each bit position have a bounded
// number of collisions (approximately 8 at default load factor).
h ^= (h >>> 20) ^ (h >>> 12);
return h ^ (h >>> 7) ^ (h >>> 4);
}
谁能告诉我,为什么这个哈希方法要这样设计?有什么好处?
最佳答案
如果您看到 Open JDK Source ,
这个方法有注释...
/**
* Applies a supplemental hash function to a given hashCode, which
* defends against poor quality hash functions. This is critical
* because HashMap uses power-of-two length hash tables, that
* otherwise encounter collisions for hashCodes that do not differ
* in lower bits. Note: Null keys always map to hash 0, thus index 0.
*/
关于java - 为什么HashMap的方法hash(int h)是这样的呢?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17780090/