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  • 【JAVA笔记——道】泛型接口设计(未完成)

    Hadoop设计模式–接口类

    泛型接口设计

    WritableComparator 相信大家都不会陌生,在MapReduce Shuffle中经常会被用到。因此摘自WritableComparator中Hadoop中优秀的设计模式,一方面好记星不如烂笔头,方便自用,一方面分享大家。

    public class WritableComparator implements RawComparator, Configurable {
        ...
      /** For backwards compatibility. **/
      public static WritableComparator get(Class<? extends WritableComparable> c) {
        return get(c, null);
      }
    
      /** Get a comparator for a {@link WritableComparable} implementation. */
      public static WritableComparator get(
          Class<? extends WritableComparable> c, Configuration conf) {
        WritableComparator comparator = comparators.get(c);
        if (comparator == null) {
          // force the static initializers to run
          forceInit(c);
          // look to see if it is defined now
          comparator = comparators.get(c);
          // if not, use the generic one
          if (comparator == null) {
            comparator = new WritableComparator(c, conf, true);
          }
        }
        // Newly passed Configuration objects should be used.
        ReflectionUtils.setConf(comparator, conf);
        return comparator;
      }
        ...

    WritableComparator 提供两种get方法,主要的参数Class< ? extends WritableComparable> c,get方法会对传入的class 进行比较操作

    之前写了一半,电脑挂了,后续补

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  • 原文地址:https://www.cnblogs.com/cunchen/p/9464177.html
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