| /******************************************************************************* |
| * Copyright (c) 2007, 2009 IBM Corporation and others. |
| * 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: |
| * IBM Corporation - initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.core.internal.databinding.observable; |
| |
| /** |
| * Created to avoid a dependency on java.util.LinkedList, see bug 205224. |
| * |
| * @since 1.1 |
| * |
| */ |
| public class Queue { |
| |
| static class Entry { |
| Object object; |
| |
| Entry(Object o) { |
| this.object = o; |
| } |
| |
| Entry next; |
| } |
| |
| Entry first; |
| Entry last; |
| |
| /** |
| * Adds the given object to the end of the queue. |
| * |
| * @param o |
| */ |
| public void enqueue(Object o) { |
| Entry oldLast = last; |
| last = new Entry(o); |
| if (oldLast != null) { |
| oldLast.next = last; |
| } else { |
| first = last; |
| } |
| } |
| |
| /** |
| * Returns the first object in the queue. The queue must not be empty. |
| * |
| * @return the first object |
| */ |
| public Object dequeue() { |
| Entry oldFirst = first; |
| if (oldFirst == null) { |
| throw new IllegalStateException(); |
| } |
| first = oldFirst.next; |
| if (first == null) { |
| last = null; |
| } |
| oldFirst.next = null; |
| return oldFirst.object; |
| } |
| |
| /** |
| * Returns <code>true</code> if the list is empty. |
| * |
| * @return <code>true</code> if the list is empty |
| */ |
| public boolean isEmpty() { |
| return first == null; |
| } |
| } |