org.apache.hadoop.examples
Class WordCount.Reduce

java.lang.Object
  org.apache.hadoop.mapred.MapReduceBase
      org.apache.hadoop.examples.WordCount.Reduce

All Implemented Interfaces:

Closeable, JobConfigurable, Reducer

Enclosing class:

WordCount

public static class WordCount.Reduce
extends MapReduceBase
implements Reducer

A reducer class that just emits the sum of the input values.

Constructor Summary

WordCount.Reduce()

Method Summary

void	reduce(WritableComparable key, Iterator values, OutputCollector output, Reporter reporter) Combines values for a given key.

Methods inherited from class org.apache.hadoop.mapred.MapReduceBase

close, configure

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.hadoop.mapred.JobConfigurable

configure

Methods inherited from interface org.apache.hadoop.io.Closeable

close

Constructor Detail

WordCount.Reduce

public WordCount.Reduce()

Method Detail

reduce

public void reduce(WritableComparable key,
                   Iterator values,
                   OutputCollector output,
                   Reporter reporter)
            throws IOException

Description copied from interface: Reducer

Combines values for a given key. Output values must be of the same type as input values. Input keys must not be altered. Typically all values are combined into zero or one value. Output pairs are collected with calls to OutputCollector.collect(WritableComparable,Writable).

Specified by:

reduce in interface Reducer

Parameters:

key - the key

values - the values to combine

output - to collect combined values

Throws:

IOException