Java常用HASH算法总结【经典实例】

/**
* Hash算法大全

* 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>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> 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> 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> 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> 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;
  }
}