| /******************************************************************************* |
| * Copyright (c) 2005, 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.iterators; |
| |
| import java.util.ListIterator; |
| import java.util.NoSuchElementException; |
| import org.eclipse.jpt.utility.internal.StringTools; |
| |
| /** |
| * A <code>SingleElementListIterator</code> holds a single element |
| * and returns it with the first call to {@link next()}, at |
| * which point it will return <code>false</code> to any subsequent |
| * call to {@link #hasNext()}. Likewise, it will return <code>false</code> |
| * to a call to {@link #hasPrevious()} until a call to {@link #next()}, |
| * at which point a call to {@link #previous()} will return the |
| * single element. |
| * <p> |
| * A <code>SingleElementListIterator</code> is equivalent to the |
| * {@link Iterator} returned by: |
| * {@link java.util.Collections#singletonList(element)}<code>.listIterator()</code> |
| * |
| * @param <E> the type of elements returned by the iterator |
| * |
| * @see org.eclipse.jpt.utility.internal.iterables.SingleElementListIterable |
| */ |
| public class SingleElementListIterator<E> |
| implements ListIterator<E> |
| { |
| private final E element; |
| private boolean hasNext; |
| |
| |
| /** |
| * Construct a list iterator that returns only the specified element. |
| */ |
| public SingleElementListIterator(E element) { |
| super(); |
| this.element = element; |
| this.hasNext = true; |
| } |
| |
| public boolean hasNext() { |
| return this.hasNext; |
| } |
| |
| public E next() { |
| if (this.hasNext) { |
| this.hasNext = false; |
| return this.element; |
| } |
| throw new NoSuchElementException(); |
| } |
| |
| public int nextIndex() { |
| return this.hasNext ? 0 : 1; |
| } |
| |
| public boolean hasPrevious() { |
| return ! this.hasNext; |
| } |
| |
| public E previous() { |
| if (this.hasNext) { |
| throw new NoSuchElementException(); |
| } |
| this.hasNext = true; |
| return this.element; |
| } |
| |
| public int previousIndex() { |
| return this.hasNext ? -1 : 0; |
| } |
| |
| public void add(E e) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public void set(E e) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| public void remove() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| @Override |
| public String toString() { |
| return StringTools.buildToStringFor(this, this.element); |
| } |
| |
| } |