理解散列码 [英] understanding of hash code

问题描述

哈希函数在实现哈希表中很重要。我知道在java
Object中有它的哈希代码，它可能是由弱哈希函数产生的。

以下是一个片段，它是补充散列函数

  static int hash（Object x）{
 int h = x.hashCode（）; 
 
 h + =〜（h <9）; 
 h ^ =（h>>> 14）; 
 h + =（h <4）; 
 h ^ =（h>>> 10）; 
返回h; 
 
 
 
 
 
 $ b 
任何人都可以帮助解释散列算法的基本思想是什么
？生成非重复的整数？如果是这样，那么这些按位
操作是如何实现的呢？ 
 
解决方案
哈希函数是任何定义良好的过程，数学函数，将大量的可能大小可变的数据转换为小数据，通常是一个可用作数组索引的整数。由散列函数返回的值称为散列值，散列码，散列总和，校验和或简单散列。 （维基百科）
 
 
 
使用更多人语言对象散列是基于对象属性的简短紧凑值。这就是说，如果你有两个对象以某种方式变化 - 你可以期望他们的散列值是不同的。好的散列算法为不同的对象产生不同的值。  
hash function is important in implementing hash table. I know that in java
Object has its hash code, which might be generated from weak hash function.

Following is one snippet that is "supplement hash function"
static int hash(Object x) {
    int h = x.hashCode();

    h += ~(h << 9);
    h ^=  (h >>> 14);
    h +=  (h << 4);
    h ^=  (h >>> 10);
    return h;
}
Can anybody help to explain what is the fundamental idea of a hash algorithm
? to generate non-duplicate integer? If so, how does these bitwise
operations make it?
解决方案
A hash function is any well-defined procedure or mathematical function that converts a large, possibly variable-sized amount of data into a small datum, usually a single integer that may serve as an index to an array. The values returned by a hash function are called hash values, hash codes, hash sums, checksums or simply hashes. (wikipedia)

Using more "human" language object hash is a short and compact value based on object's properties. That is if you have two objects that vary somehow - you can expect their hash values to be different. Good hash algorithm produces different values for different objects. 

                        
这篇关于理解散列码的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！