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ParallelJ is a Java framework for parallel computing. It provides flow modeling and execution. This project contains the core of ParallelJ which brings the execution engine, but also all the elements you need to define a ParallelJ program: annotations, libraries, etc.

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/*
 *     ParallelJ, framework for parallel computing
 *
 *     Copyright (C) 2010, 2011, 2012 Atos Worldline or third-party contributors as
 *     indicated by the @author tags or express copyright attribution
 *     statements applied by the authors.
 *
 *     This library is free software; you can redistribute it and/or
 *     modify it under the terms of the GNU Lesser General Public
 *     License as published by the Free Software Foundation; either
 *     version 2.1 of the License.
 *
 *     This library is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *     Lesser General Public License for more details.
 *
 *     You should have received a copy of the GNU Lesser General Public
 *     License along with this library; if not, write to the Free Software
 *     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
package org.parallelj.util;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * {@link BatchIterable} converts an {@link Iterable} of elements into an
 * {@link Iterable} of {@link Iterable} of elements.
 * 
 * It allows to process elements by batch of elements instead of element by
 * element.
 * 
 * @author Atos Worldline
 * 
 * @param 
 */
public class BatchIterable implements Iterable> {

	/**
	 * The default batch size
	 */
	public static final int DEFAULT_SIZE = 32;

	class IteratorImpl implements Iterator> {

		Iterator iterator = BatchIterable.this.iterable.iterator();

		public boolean hasNext() {
			return this.iterator.hasNext();
		}

		public Iterable next() {
			if (!this.hasNext()) {
				throw new NoSuchElementException();
			}
			List list = new ArrayList();
			for (int i = 0; i < BatchIterable.this.size; i++) {
				if (this.iterator.hasNext()) {
					list.add(this.iterator.next());
				} else {
					break;
				}
			}
			return list;
		}

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

	}

	/**
	 * The iterable to convert.
	 */
	private Iterable iterable;

	/**
	 * The batch size.
	 */
	private int size;

	/**
	 * Create a {@link BatchIterable} with a default batch size.
	 * 
	 * @param iterable
	 * @see #DEFAULT_SIZE
	 * @see BatchIterable#DemuxIterable(Iterable, int)
	 */
	public BatchIterable(Iterable iterable) {
		this(iterable, DEFAULT_SIZE);
	}

	/**
	 * Create a {@link BatchIterable}
	 * 
	 * @param iterable
	 *            the iterable to convert
	 * @param size
	 *            the batch size
	 * 
	 * @throws IllegalArgumentException
	 *             if iterable is null or if size is <= 0
	 */
	public BatchIterable(Iterable iterable, int size) {
		if (iterable == null) {
			throw new IllegalArgumentException("iterable must be != null");
		}
		if (size <= 0) {
			throw new IllegalArgumentException("size must be > 0");
		}
		this.iterable = new BufferedIterable(iterable, 2 * size);
		this.size = size;
	}

	@Override
	public Iterator> iterator() {
		return new IteratorImpl();
	}

}