org.apache.hadoop.mapreduce
Interfaces 
Counter
CounterGroup
JobContext
MapContext
ReduceContext
TaskAttemptContext
TaskInputOutputContext
Classes 
Cluster
ClusterMetrics
Counters
ID
InputFormat
InputSplit
Job
JobID
JobStatus
Mapper
MarkableIterator
OutputCommitter
OutputFormat
Partitioner
QueueAclsInfo
QueueInfo
RecordReader
RecordWriter
Reducer
TaskAttemptID
TaskCompletionEvent
TaskID
TaskTrackerInfo
Enums 
JobCounter
JobPriority
QueueState
TaskCompletionEvent.Status
TaskCounter
TaskType