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## org.apache.hadoop.mapreduce.lib.map
Class MultithreadedMapper<K1,V1,K2,V2>

    java.lang.Object
      org.apache.hadoop.mapreduce.Mapper<K1,V1,K2,V2>
          org.apache.hadoop.mapreduce.lib.map.MultithreadedMapper<K1,V1,K2,V2>

    public class MultithreadedMapper<K1,V1,K2,V2>

extends Mapper<K1,V1,K2,V2>

Multithreaded implementation for @link org.apache.hadoop.mapreduce.Mapper.

It can be used instead of the default implementation,

Nested Class Summary

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

Constructor Summary
`MultithreadedMapper()`

Method Summary
`static
`<K1,V1,K2,V2> Class<Mapper<K1,V1,K2,V2>>`
` | `getMapperClass(JobContext job)` Get the application's mapper class.
`static int` | `getNumberOfThreads(JobContext job)` The number of threads in the thread pool that will run the map function.
`void` | `run(Mapper.Context context)` Run the application's maps using a thread pool.
`static
`<K1,V1,K2,V2> void`
` | `setMapperClass(Job job, Class<? extends Mapper<K1,V1,K2,V2>> cls)` Set the application's mapper class.
`static void` | `setNumberOfThreads(Job job, int threads)` Set the number of threads in the pool for running maps.

Methods inherited from class org.apache.hadoop.mapreduce.Mapper
`cleanup, map, setup`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### MultithreadedMapper

    public MultithreadedMapper()

Method Detail

### getNumberOfThreads

    public static int getNumberOfThreads(JobContext job)

  The number of threads in the thread pool that will run the map function.

  Parameters:
    `job` - the job
  Returns:
    the number of threads

### setNumberOfThreads

    public static void setNumberOfThreads(Job job,
                                          int threads)

  Set the number of threads in the pool for running maps.

  Parameters:
    `job` - the job to modify
    `threads` - the new number of threads

### getMapperClass

    public static <K1,V1,K2,V2> Class<Mapper<K1,V1,K2,V2>> getMapperClass(JobContext job)

  Get the application's mapper class.

  Type Parameters:
    `K1` - the map's input key type
    `V1` - the map's input value type
    `K2` - the map's output key type
    `V2` - the map's output value type
  Parameters:
    `job` - the job
  Returns:
    the mapper class to run

### setMapperClass

    public static <K1,V1,K2,V2> void setMapperClass(Job job,
                                                    Class<? extends Mapper<K1,V1,K2,V2>> cls)

  Set the application's mapper class.

  Type Parameters:
    `K1` - the map input key type
    `V1` - the map input value type
    `K2` - the map output key type
    `V2` - the map output value type
  Parameters:
    `job` - the job to modify
    `cls` - the class to use as the mapper

### run

    public void run(Mapper.Context context)
             throws IOException,
                    InterruptedException

  Run the application's maps using a thread pool.

  Overrides:
    `run` in class `Mapper<K1,V1,K2,V2>`
  Throws:
    `IOException`
    `InterruptedException`

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Copyright © 2009 The Apache Software Foundation