CompositeRecordReader.java 文件源码

/**
 * Add a RecordReader to this collection.
 * The id() of a RecordReader determines where in the Tuple its
 * entry will appear. Adding RecordReaders with the same id has
 * undefined behavior.
 */
public void add(ComposableRecordReader<K,? extends V> rr) throws IOException {
  kids[rr.id()] = rr;
  if (null == q) {
    cmp = WritableComparator.get(rr.createKey().getClass(), conf);
    q = new PriorityQueue<ComposableRecordReader<K,?>>(3,
        new Comparator<ComposableRecordReader<K,?>>() {
          public int compare(ComposableRecordReader<K,?> o1,
                             ComposableRecordReader<K,?> o2) {
            return cmp.compare(o1.key(), o2.key());
          }
        });
  }
  if (rr.hasNext()) {
    q.add(rr);
  }
}