jpa/plugins/org.eclipse.jpt.utility/src/org/eclipse/jpt/utility/internal/iterables/EmptyIterable.java

/*******************************************************************************
 * Copyright (c) 2009 Oracle. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0, which accompanies this distribution
 * and is available at http://www.eclipse.org/legal/epl-v10.html.
 * 
 * Contributors:
 *     Oracle - initial API and implementation
 ******************************************************************************/
package org.eclipse.jpt.utility.internal.iterables;

import java.util.Iterator;

import org.eclipse.jpt.utility.internal.StringTools;
import org.eclipse.jpt.utility.internal.iterators.EmptyIterator;

/**
 * An <code>EmptyIterable</code> is just that.
 * Maybe just a touch better-performing than java.util.Collections.EMPTY_SET
 * since we don't create a new Iterator every time #iterator() is called.
 * (Not sure why they do that....)
 * 
 * @see EmptyIterator
 */
public final class EmptyIterable<E>
	implements Iterable<E>
{
	// singleton
	@SuppressWarnings("unchecked")
	private static final Iterable INSTANCE = new EmptyIterable();

	/**
	 * Return the singleton.
	 */
	@SuppressWarnings("unchecked")
	public static <T> Iterable<T> instance() {
		return INSTANCE;
	}

	/**
	 * Ensure single instance.
	 */
	private EmptyIterable() {
		super();
	}

	public Iterator<E> iterator() {
		return EmptyIterator.instance();
	}

	@Override
	public String toString() {
		return StringTools.buildToStringFor(this);
	}

}