TestJobCounters.java 文件源码

public void reduce(WritableComparable key, Iterator<Writable> val, 
                   OutputCollector<WritableComparable, Writable> output,
                   Reporter reporter)
throws IOException {
  assertNotNull("Reducer not configured!", loader);

  // load the memory
  loader.load();

  // work as identity reducer
  output.collect(key, key);
}