| Interface | Description | 
|---|---|
| InputFormat<K,V> | InputFormatdescribes the input-specification for a 
 Map-Reduce job. | 
| InputSplit | InputSplitrepresents the data to be processed by an 
 individualMapper. | 
| InputSplitWithLocationInfo | |
| JobConfigurable | That what may be configured. | 
| JobContext | |
| Mapper<K1,V1,K2,V2> | Maps input key/value pairs to a set of intermediate key/value pairs. | 
| MapRunnable<K1,V1,K2,V2> | Expert: Generic interface for  Mappers. | 
| OutputCollector<K,V> | |
| OutputFormat<K,V> | OutputFormatdescribes the output-specification for a 
 Map-Reduce job. | 
| Partitioner<K2,V2> | Partitions the key space. | 
| RecordReader<K,V> | RecordReaderreads <key, value> pairs from anInputSplit. | 
| RecordWriter<K,V> | RecordWriterwrites the output <key, value> pairs 
 to an output file. | 
| Reducer<K2,V2,K3,V3> | Reduces a set of intermediate values which share a key to a smaller set of
 values. | 
| Reporter | A facility for Map-Reduce applications to report progress and update 
 counters, status information etc. | 
| RunningJob | RunningJobis the user-interface to query for details on a 
 running Map-Reduce job. | 
| TaskAttemptContext | 
| Class | Description | 
|---|---|
| ClusterStatus | Status information on the current state of the Map-Reduce cluster. | 
| Counters | A set of named counters. | 
| Counters.Counter | A counter record, comprising its name and value. | 
| Counters.Group | Groupof counters, comprising of counters from a particular
  counterEnumclass. | 
| FileInputFormat<K,V> | A base class for file-based  InputFormat. | 
| FileOutputCommitter | An  OutputCommitterthat commits files specified 
 in job output directory i.e. | 
| FileOutputFormat<K,V> | A base class for  OutputFormat. | 
| FileSplit | A section of an input file. | 
| FixedLengthInputFormat | FixedLengthInputFormat is an input format used to read input files
 which contain fixed length records. | 
| ID | A general identifier, which internally stores the id
 as an integer. | 
| JobClient | JobClientis the primary interface for the user-job to interact
 with the cluster. | 
| JobConf | A map/reduce job configuration. | 
| JobID | JobID represents the immutable and unique identifier for 
 the job. | 
| JobQueueInfo | Class that contains the information regarding the Job Queues which are 
 maintained by the Hadoop Map/Reduce framework. | 
| JobStatus | Describes the current status of a job. | 
| KeyValueLineRecordReader | This class treats a line in the input as a key/value pair separated by a 
 separator character. | 
| KeyValueTextInputFormat | An  InputFormatfor plain text files. | 
| MapFileOutputFormat | An  OutputFormatthat writesMapFiles. | 
| MapReduceBase | |
| MapRunner<K1,V1,K2,V2> | Default  MapRunnableimplementation. | 
| MultiFileInputFormat<K,V> | An abstract  InputFormatthat returnsMultiFileSplit's
 inMultiFileInputFormat.getSplits(JobConf, int)method. | 
| MultiFileSplit | A sub-collection of input files. | 
| OutputCommitter | OutputCommitterdescribes the commit of task output for a 
 Map-Reduce job. | 
| OutputLogFilter | This class filters log files from directory given
 It doesnt accept paths having _logs. | 
| SequenceFileAsBinaryInputFormat | InputFormat reading keys, values from SequenceFiles in binary (raw)
 format. | 
| SequenceFileAsBinaryOutputFormat | An  OutputFormatthat writes keys, values toSequenceFiles in binary(raw) format | 
| SequenceFileAsTextInputFormat | This class is similar to SequenceFileInputFormat, 
 except it generates SequenceFileAsTextRecordReader 
 which converts the input keys and values to their 
 String forms by calling toString() method. | 
| SequenceFileAsTextRecordReader | This class converts the input keys and values to their String forms by calling toString()
 method. | 
| SequenceFileInputFilter<K,V> | A class that allows a map/red job to work on a sample of sequence files. | 
| SequenceFileInputFormat<K,V> | An  InputFormatforSequenceFiles. | 
| SequenceFileOutputFormat<K,V> | An  OutputFormatthat writesSequenceFiles. | 
| SequenceFileRecordReader<K,V> | An  RecordReaderforSequenceFiles. | 
| SkipBadRecords | Utility class for skip bad records functionality. | 
| SplitLocationInfo | |
| TaskAttemptID | TaskAttemptID represents the immutable and unique identifier for 
 a task attempt. | 
| TaskCompletionEvent | This is used to track task completion events on 
 job tracker. | 
| TaskID | TaskID represents the immutable and unique identifier for 
 a Map or Reduce Task. | 
| TaskReport | A report on the state of a task. | 
| TextInputFormat | An  InputFormatfor plain text files. | 
| TextOutputFormat<K,V> | An  OutputFormatthat writes plain text files. | 
| Utils | A utility class. | 
| Enum | Description | 
|---|---|
| JobPriority | Used to describe the priority of the running job. | 
| TaskCompletionEvent.Status | 
| Exception | Description | 
|---|---|
| FileAlreadyExistsException | Used when target file already exists for any operation and 
 is not configured to be overwritten. | 
| InvalidFileTypeException | Used when file type differs from the desired file type. | 
| InvalidInputException | This class wraps a list of problems with the input, so that the user
 can get a list of problems together instead of finding and fixing them one 
 by one. | 
| InvalidJobConfException | This exception is thrown when jobconf misses some mendatory attributes
 or value of some attributes is invalid. | 
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