Java中常用hash算法总结

/**
 * Hash算法大全<br>
 * 推荐使用FNV1算法
 * @author hsfxuebao
 */
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;
  }
 
  /**
   * 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;
  }
}