Re: Efficiently sequencing a stream of objects

Chris wrote:


Not all cast are there. Compare your version with "genericified" one
(attached below).

piotr

--
public class MergingIterator<E extends Comparable<? super E>> implements
Iterator<E> {
   private PriorityQueue<Carrier> queue = new PriorityQueue<Carrier>();

   public void add(Iterator<? extends E> it) {
     if (!it.hasNext())
       return; // do nothing, do not add

     Carrier carrier = new Carrier();
     carrier.it = it;
     carrier.next = it.next();
     queue.offer(carrier);
   }

   public boolean hasNext() {
     return !queue.isEmpty();
   }

   public E next() {
      Carrier carrier = queue.poll();
      E next = carrier.next;

      // if there's another object to be had from this stream, insert it.
      // if not, the queue just gets smaller
      if (carrier.it.hasNext()) {
        carrier.next = carrier.it.next();
        queue.offer(carrier);
      }

      return next;
   }

   public void remove() {
     throw new UnsupportedOperationException();
   }

   private class Carrier implements Comparable<Carrier> {
     Iterator<? extends E> it;
     E next;

     public int compareTo(Carrier other) {
       return next.compareTo(other.next);
     }
   }
}