@Override
  public ByteBuffer getQualifierByteBuffer() {
    if (cell instanceof ByteBufferExtendedCell) {
      return ((ByteBufferExtendedCell) this.cell).getQualifierByteBuffer();
    } else {
      return ByteBuffer.wrap(CellUtil.cloneQualifier(this.cell));
    }
  }
A wrapper for a cell to be used with mapreduce, as the output value class for mappers/reducers.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/util/MapReduceExtendedCell.java