| /******************************************************************************* |
| * Copyright (c) 2008, 2010 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.common.utility.internal.iterables; |
| |
| import java.io.Serializable; |
| import java.util.Iterator; |
| |
| import org.eclipse.jpt.common.utility.internal.iterators.EmptyIterator; |
| |
| /** |
| * An <code>EmptyIterable</code> is just that. |
| * Maybe just a touch better-performing than {@link java.util.Collections#EMPTY_SET} |
| * since we don't create a new {@link Iterator} every time {@link #iterator()} is called. |
| * (Not sure why they do that....) |
| * |
| * @param <E> the type of elements returned by the iterable's iterator |
| * |
| * @see EmptyIterator |
| * @see EmptyListIterable |
| */ |
| public final class EmptyIterable<E> |
| implements Iterable<E>, Serializable |
| { |
| // singleton |
| @SuppressWarnings("rawtypes") |
| 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 this.getClass().getSimpleName(); |
| } |
| |
| private static final long serialVersionUID = 1L; |
| private Object readResolve() { |
| // replace this object with the singleton |
| return INSTANCE; |
| } |
| |
| } |