org.eigenbase.runtime
Class ThreadIterator

java.lang.Object
  org.eigenbase.runtime.QueueIterator
      org.eigenbase.runtime.ThreadIterator

All Implemented Interfaces:

Runnable, Iterator, Iterable

Direct Known Subclasses:

FarragoJavaUdxIterator, ThreadIteratorTest.ArrayIterator

public abstract class ThreadIterator
extends QueueIterator
implements Iterator, Runnable, Iterable

ThreadIterator converts 'push' code to 'pull'. You implement doWork() to call QueueIterator.put(java.lang.Object) with each row, and this class invokes it in a separate thread. Then the results come out via the familiar Iterator interface. For example,

class ArrayIterator extends ThreadIterator {
   Object[] a;
   ArrayIterator(Object[] a) {
     this.a = a;
     start();
   }
   protected void doWork() {
     for (int i = 0; i < a.length; i++) {
       put(a[i]);
     }
   }
 }

Or, more typically, using an anonymous class:

Iterator i = new ThreadIterator() {
   int limit;
   public ThreadIterator start(int limit) {
     this.limit = limit;
     return super.start();
   }
   protected void doWork() {
     for (int i = 0; i < limit; i++) {
       put(new Integer(i));
     }
   }
 }.start(100);
 while (i.hasNext()) {
   etc.
 }

Nested Class Summary

Nested classes/interfaces inherited from class org.eigenbase.runtime.QueueIterator

QueueIterator.TimeoutException

Field Summary

private Thread

thread

Fields inherited from class org.eigenbase.runtime.QueueIterator

hasNext, next, queue, throwable

Constructor Summary

ThreadIterator()

ThreadIterator(BlockingQueue queue)

Method Summary

protected abstract void	doWork() The implementation should call QueueIterator.put(java.lang.Object) with each row.
Iterator	iterator() Returns an iterator over the elements in this collection.
protected void	onEndOfQueue() Called (from the consumer thread context) just before the iterator returns false for hasNext().
void	run()
protected ThreadIterator	start()

Methods inherited from class org.eigenbase.runtime.QueueIterator

checkTermination, done, hasNext, hasNext, next, next, offer, put, remove, reset

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Iterator

hasNext, next, remove

Field Detail

thread

private Thread thread

Constructor Detail

ThreadIterator

public ThreadIterator()

ThreadIterator

public ThreadIterator(BlockingQueue queue)

Method Detail

iterator

public Iterator iterator()

Description copied from interface: Iterable

Returns an iterator over the elements in this collection. There are no guarantees over the order in which the elements are returned.

If this method is called twice on the same object, and the object is not modified in between times, the iterators produced may or may not be the same iterator, and may or may not return the elements in the same order, but must return the same objects.

Specified by:

iterator in interface Iterable

run

public void run()

Specified by:

run in interface Runnable

doWork

protected abstract void doWork()

The implementation should call QueueIterator.put(java.lang.Object) with each row.

start

protected ThreadIterator start()

onEndOfQueue

protected void onEndOfQueue()

Description copied from class: QueueIterator

Called (from the consumer thread context) just before the iterator returns false for hasNext(). Default implementation does nothing, but subclasses can use this for cleanup actions.

Overrides:

onEndOfQueue in class QueueIterator