这篇文章主要介绍了java常用hash算法,结合实例形式总结分析了java常用的hash算法,包括加法hash、旋转hash、fnv算法、rs算法hash、pjw算法、elf算法、bkdr算法、sdbm算法、djb算法、dek算法、ap算法等,需要的朋友可以参考下
本文实例讲述了java常用hash算法。分享给大家供大家参考，具体如下：
/**
* hash算法大全<br>
* 推荐使用fnv1算法
* @algorithm none
* @author goodzzp 2006-11-20
* @lastedit goodzzp 2006-11-20
* @editdetail create
*/
public class hashalgorithms
{
/**//**
* 加法hash
* @param key 字符串
* @param prime 一个质数
* @return hash结果
*/
public static int additivehash(string key, int prime)
{
int hash, i;
for (hash = key.length(), i = 0; i < key.length(); i++)
hash += key.charat(i);
return (hash % prime);
}
/**//**
* 旋转hash
* @param key 输入字符串
* @param prime 质数
* @return hash值
*/
public static int rotatinghash(string key, int prime)
{
int hash, i;
for (hash=key.length(), i=0; i<key.length(); ++i)
hash = (hash<<4)^(hash>>28)^key.charat(i);
return (hash % prime);
// return (hash ^ (hash>>10) ^ (hash>>20));
}
// 替代：
// 使用：hash = (hash ^ (hash>>10) ^ (hash>>20)) & mask;
// 替代：hash %= prime;
/**//**
* mask值，随便找一个值，最好是质数
*/
static int m_mask = 0x8765fed1;
/**//**
* 一次一个hash
* @param key 输入字符串
* @return 输出hash值
*/
public static int onebyonehash(string key)
{
int hash, i;
for (hash=0, i=0; i<key.length(); ++i)
{
hash += key.charat(i);
hash += (hash << 10);
hash ^= (hash >> 6);
}
hash += (hash << 3);
hash ^= (hash >> 11);
hash += (hash << 15);
// return (hash & m_mask);
return hash;
}
/**//**
* bernstein's hash
* @param key 输入字节数组
* @param level 初始hash常量
* @return 结果hash
*/
public static int bernstein(string key)
{
int hash = 0;
int i;
for (i=0; i<key.length(); ++i) hash = 33*hash + key.charat(i);
return hash;
}
//
/**///// pearson's hash
// char pearson(char[]key, ub4 len, char tab[256])
// {
// char hash;
// ub4 i;
// for (hash=len, i=0; i<len; ++i)
// hash=tab[hash^key[i]];
// return (hash);
// }
/**///// crc hashing，计算crc,具体代码见其他
// ub4 crc(char *key, ub4 len, ub4 mask, ub4 tab[256])
// {
// ub4 hash, i;
// for (hash=len, i=0; i<len; ++i)
// hash = (hash >> 8) ^ tab[(hash & 0xff) ^ key[i]];
// return (hash & mask);
// }
/**//**
* universal hashing
*/
public static int universal(char[]key, int mask, int[] tab)
{
int hash = key.length, i, len = key.length;
for (i=0; i<(len<<3); i+=8)
{
char k = key[i>>3];
if ((k&0x01) == 0) hash ^= tab[i+0];
if ((k&0x02) == 0) hash ^= tab[i+1];
if ((k&0x04) == 0) hash ^= tab[i+2];
if ((k&0x08) == 0) hash ^= tab[i+3];
if ((k&0x10) == 0) hash ^= tab[i+4];
if ((k&0x20) == 0) hash ^= tab[i+5];
if ((k&0x40) == 0) hash ^= tab[i+6];
if ((k&0x80) == 0) hash ^= tab[i+7];
}
return (hash & mask);
}
/**//**
* zobrist hashing
*/
public static int zobrist( char[] key,int mask, int[][] tab)
{
int hash, i;
for (hash=key.length, i=0; i<key.length; ++i)
hash ^= tab[i][key[i]];
return (hash & mask);
}
// lookup3
// 见bob jenkins(3).c文件
// 32位fnv算法
static int m_shift = 0;
/**//**
* 32位的fnv算法
* @param data 数组
* @return int值
*/
public static int fnvhash(byte[] data)
{
int hash = (int)2166136261l;
for(byte b : data)
hash = (hash * 16777619) ^ b;
if (m_shift == 0)
return hash;
return (hash ^ (hash >> m_shift)) & m_mask;
}
/**//**
* 改进的32位fnv算法1
* @param data 数组
* @return int值
*/
public static int fnvhash1(byte[] data)
{
final int p = 16777619;
int hash = (int)2166136261l;
for(byte b:data)
hash = (hash ^ b) * p;
hash += hash << 13;
hash ^= hash >> 7;
hash += hash << 3;
hash ^= hash >> 17;
hash += hash << 5;
return hash;
}
/**//**
* 改进的32位fnv算法1
* @param data 字符串
* @return int值
*/
public static int fnvhash1(string data)
{
final int p = 16777619;
int hash = (int)2166136261l;
for(int i=0;i<data.length();i++)
hash = (hash ^ data.charat(i)) * p;
hash += hash << 13;
hash ^= hash >> 7;
hash += hash << 3;
hash ^= hash >> 17;
hash += hash << 5;
return hash;
}
/**//**
* thomas wang的算法，整数hash
*/
public static int inthash(int key)
{
key += ~(key << 15);
key ^= (key >>> 10);
key += (key << 3);
key ^= (key >>> 6);
key += ~(key << 11);
key ^= (key >>> 16);
return key;
}
/**//**
* rs算法hash
* @param str 字符串
*/
public static int rshash(string str)
{
int b = 378551;
int a = 63689;
int hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash = hash * a + str.charat(i);
a = a * b;
}
return (hash & 0x7fffffff);
}
/**//* end of rs hash function */
/**//**
* js算法
*/
public static int jshash(string str)
{
int hash = 1315423911;
for(int i = 0; i < str.length(); i++)
{
hash ^= ((hash << 5) + str.charat(i) + (hash >> 2));
}
return (hash & 0x7fffffff);
}
/**//* end of js hash function */
/**//**
* pjw算法
*/
public static int pjwhash(string str)
{
int bitsinunsignedint = 32;
int threequarters = (bitsinunsignedint * 3) / 4;
int oneeighth = bitsinunsignedint / 8;
int highbits = 0xffffffff << (bitsinunsignedint - oneeighth);
int hash = 0;
int test = 0;
for(int i = 0; i < str.length();i++)
{
hash = (hash << oneeighth) + str.charat(i);
if((test = hash & highbits) != 0)
{
hash = (( hash ^ (test >> threequarters)) & (~highbits));
}
}
return (hash & 0x7fffffff);
}
/**//* end of p. j. weinberger hash function */
/**//**
* elf算法
*/
public static int elfhash(string str)
{
int hash = 0;
int x = 0;
for(int i = 0; i < str.length(); i++)
{
hash = (hash << 4) + str.charat(i);
if((x = (int)(hash & 0xf0000000l)) != 0)
{
hash ^= (x >> 24);
hash &= ~x;
}
}
return (hash & 0x7fffffff);
}
/**//* end of elf hash function */
/**//**
* bkdr算法
*/
public static int bkdrhash(string str)
{
int seed = 131; // 31 131 1313 13131 131313 etc..
int hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash = (hash * seed) + str.charat(i);
}
return (hash & 0x7fffffff);
}
/**//* end of bkdr hash function */
/**//**
* sdbm算法
*/
public static int sdbmhash(string str)
{
int hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash = str.charat(i) + (hash << 6) + (hash << 16) - hash;
}
return (hash & 0x7fffffff);
}
/**//* end of sdbm hash function */
/**//**
* djb算法
*/
public static int djbhash(string str)
{
int hash = 5381;
for(int i = 0; i < str.length(); i++)
{
hash = ((hash << 5) + hash) + str.charat(i);
}
return (hash & 0x7fffffff);
}
/**//* end of djb hash function */
/**//**
* dek算法
*/
public static int dekhash(string str)
{
int hash = str.length();
for(int i = 0; i < str.length(); i++)
{
hash = ((hash << 5) ^ (hash >> 27)) ^ str.charat(i);
}
return (hash & 0x7fffffff);
}
/**//* end of dek hash function */
/**//**
* ap算法
*/
public static int aphash(string str)
{
int hash = 0;
for(int i = 0; i < str.length(); i++)
{
hash ^= ((i & 1) == 0) ? ( (hash << 7) ^ str.charat(i) ^ (hash >> 3)) :
(~((hash << 11) ^ str.charat(i) ^ (hash >> 5)));
}
// return (hash & 0x7fffffff);
return hash;
}
/**//* end of ap hash function */
/**//**
* java自己带的算法
*/
public static int java(string str)
{
int h = 0;
int off = 0;
int len = str.length();
for (int i = 0; i < len; i++)
{
h = 31 * h + str.charat(off++);
}
return h;
}
/**//**
* 混合hash算法，输出64位的值
*/
public static long mixhash(string str)
{
long hash = str.hashcode();
hash <<= 32;
hash |= fnvhash1(str);
return hash;
}
}
以上就是java中hash的算法总结的详细内容。