## Uses of Class
org.apache.hadoop.mapreduce.Reducer

- Packages that use Reducer
  Package | Description
  --- | ---
  org.apache.hadoop.mapreduce |
  org.apache.hadoop.mapreduce.lib.aggregate |
  org.apache.hadoop.mapreduce.lib.chain |
  org.apache.hadoop.mapreduce.lib.fieldsel |
  org.apache.hadoop.mapreduce.lib.reduce |

- - ### Uses of Reducer in org.apache.hadoop.mapreduce

    Methods in org.apache.hadoop.mapreduce that return types with arguments of type Reducer
    Modifier and Type | Method and Description
    --- | ---
    `Class<? extends Reducer<?,?,?,?>>` | JobContext.`getCombinerClass()` Get the combiner class for the job.
    `Class<? extends Reducer<?,?,?,?>>` | JobContext.`getReducerClass()` Get the `Reducer` class for the job.

    Method parameters in org.apache.hadoop.mapreduce with type arguments of type Reducer
    Modifier and Type | Method and Description
    --- | ---
    `void` | Job.`setCombinerClass(Class<? extends Reducer> cls)` Set the combiner class for the job.
    `void` | Job.`setReducerClass(Class<? extends Reducer> cls)` Set the `Reducer` for the job.

  - ### Uses of Reducer in org.apache.hadoop.mapreduce.lib.aggregate

    Subclasses of Reducer in org.apache.hadoop.mapreduce.lib.aggregate
    Modifier and Type | Class and Description
    --- | ---
    `class` | `ValueAggregatorCombiner<K1 extends WritableComparable<?>,V1 extends Writable>` This class implements the generic combiner of Aggregate.
    `class` | `ValueAggregatorReducer<K1 extends WritableComparable<?>,V1 extends Writable>` This class implements the generic reducer of Aggregate.

  - ### Uses of Reducer in org.apache.hadoop.mapreduce.lib.chain

    Subclasses of Reducer in org.apache.hadoop.mapreduce.lib.chain
    Modifier and Type | Class and Description
    --- | ---
    `class` | `ChainReducer<KEYIN,VALUEIN,KEYOUT,VALUEOUT>` The ChainReducer class allows to chain multiple Mapper classes after a Reducer within the Reducer task.

    Method parameters in org.apache.hadoop.mapreduce.lib.chain with type arguments of type Reducer
    Modifier and Type | Method and Description
    --- | ---
    `static void` | ChainReducer.`setReducer(Job job, Class<? extends Reducer> klass, Class<?> inputKeyClass, Class<?> inputValueClass, Class<?> outputKeyClass, Class<?> outputValueClass, Configuration reducerConf)` Sets the `Reducer` class to the chain job.

  - ### Uses of Reducer in org.apache.hadoop.mapreduce.lib.fieldsel

    Subclasses of Reducer in org.apache.hadoop.mapreduce.lib.fieldsel
    Modifier and Type | Class and Description
    --- | ---
    `class` | `FieldSelectionReducer<K,V>` This class implements a reducer class that can be used to perform field selections in a manner similar to unix cut.

  - ### Uses of Reducer in org.apache.hadoop.mapreduce.lib.reduce

    Subclasses of Reducer in org.apache.hadoop.mapreduce.lib.reduce
    Modifier and Type | Class and Description
    --- | ---
    `class` | `IntSumReducer<Key>`
    `class` | `LongSumReducer<KEY>`
    `class` | `WrappedReducer<KEYIN,VALUEIN,KEYOUT,VALUEOUT>` A `Reducer` which wraps a given one to allow for custom `Reducer.Context` implementations.

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