hadoop-compat/src/main/java/com/twitter/elephantbird/util/HadoopCompat.java
public static MapContext newMapContext(Configuration conf,
                                         TaskAttemptID taskAttemptID,
                                         RecordReader recordReader,
                                         RecordWriter recordWriter,
                                         OutputCommitter outputCommitter,
                                         StatusReporter statusReporter,
                                         InputSplit inputSplit) {
    return (MapContext) newInstance(MAP_CONTEXT_CONSTRUCTOR,
        conf, taskAttemptID, recordReader, recordWriter, outputCommitter,
        statusReporter, inputSplit);
  }
public static MapContext newMapContext(Configuration conf,
                                         TaskAttemptID taskAttemptID,
                                         RecordReader recordReader,
                                         RecordWriter recordWriter,
                                         OutputCommitter outputCommitter,
                                         StatusReporter statusReporter,
                                         InputSplit inputSplit) {
    return (MapContext) newInstance(MAP_CONTEXT_CONSTRUCTOR,
        conf, taskAttemptID, recordReader, recordWriter, outputCommitter,
        statusReporter, inputSplit);
  }
Instantiates MapContext under Hadoop 1 and MapContextImpl under Hadoop 2.