Package org.apache.hadoop.examples

Class WordStandardDeviation.WordStandardDeviationMapper

java.lang.Object

org.apache.hadoop.mapreduce.Mapper<java.lang.Object,org.apache.hadoop.io.Text,org.apache.hadoop.io.Text,org.apache.hadoop.io.LongWritable>

org.apache.hadoop.examples.WordStandardDeviation.WordStandardDeviationMapper

Enclosing class:

WordStandardDeviation

public static class WordStandardDeviation.WordStandardDeviationMapper
extends org.apache.hadoop.mapreduce.Mapper<java.lang.Object,org.apache.hadoop.io.Text,org.apache.hadoop.io.Text,org.apache.hadoop.io.LongWritable>

Maps words from line of text into 3 key-value pairs; one key-value pair for counting the word, one for counting its length, and one for counting the square of its length.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.hadoop.mapreduce.Mapper

org.apache.hadoop.mapreduce.Mapper.Context

Constructor Summary

Constructors

Constructor	Description
WordStandardDeviationMapper()

Method Summary

Modifier and Type	Method	Description
void	map(java.lang.Object key, org.apache.hadoop.io.Text value, org.apache.hadoop.mapreduce.Mapper.Context context)	Emits 3 key-value pairs for counting the word, its length, and the squares of its length.

Methods inherited from class org.apache.hadoop.mapreduce.Mapper

cleanup, run, setup

Methods inherited from class java.lang.Object

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

Constructor Detail

WordStandardDeviationMapper

public WordStandardDeviationMapper()

Method Detail

map

public void map(java.lang.Object key,
                org.apache.hadoop.io.Text value,
                org.apache.hadoop.mapreduce.Mapper.Context context)
         throws java.io.IOException,
                java.lang.InterruptedException

Emits 3 key-value pairs for counting the word, its length, and the squares of its length. Outputs are (Text, LongWritable).

Overrides:

map in class org.apache.hadoop.mapreduce.Mapper<java.lang.Object,org.apache.hadoop.io.Text,org.apache.hadoop.io.Text,org.apache.hadoop.io.LongWritable>

Parameters:

value - This will be a line of text coming in from our input file.

Throws:

java.io.IOException

java.lang.InterruptedException