Hash分析

org.apache.hadoop.util.hash

1. Hash抽象类 有两个实现类JenkinsHash与MurmurHash,默认是MurmurHash

可以通过hadoop.util.hash.type配置｛murmur，jenkins｝

2.JenkinsHash有main方法可以运行一下：

 if (args.length != 1) {
      System.err.println("Usage: JenkinsHash filename");
      System.exit(-1);
    }
    FileInputStream in = new FileInputStream(args[0]);
    byte[] bytes = new byte[512];
    int value = 0;
    //JenkinsHash hash = new JenkinsHash();//hadoop==>1215099288
    MurmurHash hash = new MurmurHash();//hadoop ==> 1721248589
    for (int length = in.read(bytes); length > 0 ; length = in.read(bytes)) {
      value = hash.hash(bytes, length, value);
    }
    System.out.println(Math.abs(value));
  }