| Name | Description | Type | Package | Framework |
| IntSumReducer | Class | org.apache.hadoop.mapreduce.lib.reduce | Apache Hadoop | |
| LongSumReducer | Class | org.apache.hadoop.mapreduce.lib.reduce | Apache Hadoop | |
| WrappedReducer | A Reducer which wraps a given one to allow for custom Reducer. | Class | org.apache.hadoop.mapreduce.lib.reduce | Apache Hadoop |