| /* |
| * Copyright 2007 Google Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| * use this file except in compliance with the License. You may obtain a copy of |
| * the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| * License for the specific language governing permissions and limitations under |
| * the License. |
| */ |
| package java.util; |
| |
| /** |
| * Skeletal implementation of the Queue interface. <a |
| * href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/AbstractQueue.html">[Sun |
| * docs]</a> |
| * |
| * @param <E> element type. |
| */ |
| public abstract class AbstractQueue<E> extends AbstractCollection<E> implements |
| Queue<E> { |
| |
| // Should not be instantiated directly. |
| protected AbstractQueue() { |
| } |
| |
| @Override |
| public boolean add(E o) { |
| if (offer(o)) { |
| return true; |
| } |
| throw new IllegalStateException("Unable to add element to queue"); |
| } |
| |
| @Override |
| public boolean addAll(Collection<? extends E> c) { |
| if (c == this) { |
| throw new IllegalArgumentException("Can't add a queue to itself"); |
| } |
| boolean modified = false; |
| for (E val : c) { |
| modified |= add(val); |
| } |
| return modified; |
| } |
| |
| @Override |
| public void clear() { |
| while (poll() != null) { |
| // empty loop |
| } |
| } |
| |
| public E element() { |
| E e = peek(); |
| if (e == null) { |
| throw new NoSuchElementException("Queue is empty"); |
| } |
| return e; |
| } |
| |
| public abstract boolean offer(E o); |
| |
| public abstract E peek(); |
| |
| public abstract E poll(); |
| |
| public E remove() { |
| E e = poll(); |
| if (e == null) { |
| throw new NoSuchElementException("Queue is empty"); |
| } |
| return e; |
| } |
| |
| } |