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Quadcap Embeddable Server |
00001 package com.quadcap.util.collections; 00002 00003 /* Copyright 1997 - 2003 Quadcap Software. All rights reserved. 00004 * 00005 * This software is distributed under the Quadcap Free Software License. 00006 * This software may be used or modified for any purpose, personal or 00007 * commercial. Open Source redistributions are permitted. Commercial 00008 * redistribution of larger works derived from, or works which bundle 00009 * this software requires a "Commercial Redistribution License"; see 00010 * http://www.quadcap.com/purchase. 00011 * 00012 * Redistributions qualify as "Open Source" under one of the following terms: 00013 * 00014 * Redistributions are made at no charge beyond the reasonable cost of 00015 * materials and delivery. 00016 * 00017 * Redistributions are accompanied by a copy of the Source Code or by an 00018 * irrevocable offer to provide a copy of the Source Code for up to three 00019 * years at the cost of materials and delivery. Such redistributions 00020 * must allow further use, modification, and redistribution of the Source 00021 * Code under substantially the same terms as this license. 00022 * 00023 * Redistributions of source code must retain the copyright notices as they 00024 * appear in each source code file, these license terms, and the 00025 * disclaimer/limitation of liability set forth as paragraph 6 below. 00026 * 00027 * Redistributions in binary form must reproduce this Copyright Notice, 00028 * these license terms, and the disclaimer/limitation of liability set 00029 * forth as paragraph 6 below, in the documentation and/or other materials 00030 * provided with the distribution. 00031 * 00032 * The Software is provided on an "AS IS" basis. No warranty is 00033 * provided that the Software is free of defects, or fit for a 00034 * particular purpose. 00035 * 00036 * Limitation of Liability. Quadcap Software shall not be liable 00037 * for any damages suffered by the Licensee or any third party resulting 00038 * from use of the Software. 00039 */ 00040 00041 /** 00042 * This class implements a queue with a capacity. 00043 * 00044 * @author Stan Bailes 00045 */ 00046 public interface Queue { 00047 /** 00048 * Specify the maximum capacity of this queue, -1 means unbounded. 00049 * 00050 * @param capacity the new capacity of the queue, or -1 to specify a 00051 * queue of unlimited size. 00052 */ 00053 public void setCapacity(int capacity); 00054 00055 /** 00056 * Return the number of items in the queue. 00057 * @return the queue's size 00058 */ 00059 public int size(); 00060 00061 /** 00062 * Add an object to the front of the queue. 00063 * 00064 * @param obj the object to add 00065 */ 00066 public void addFront(Object obj); 00067 00068 /** 00069 * Add an object to the back of the queue. 00070 * @param obj the object to add 00071 */ 00072 public void addBack(Object obj); 00073 00074 /** 00075 * Access the object at the front of the queue. Throw a runtime exception 00076 * if the queue is empty. 00077 * 00078 * @return the item at the head of the queue 00079 */ 00080 public Object head(); 00081 00082 /** 00083 * Access the object at the back of the queue. Throw a runtime exception 00084 * if the queue is empty. 00085 * 00086 * @return the item at the tail of the queue 00087 */ 00088 public Object tail(); 00089 00090 /** 00091 * Remove and return the item at the front of the queue. Throw a 00092 * runtime exception if the queue is empty. 00093 * 00094 * @return the item at the head of the queue 00095 */ 00096 public Object popFront(); 00097 00098 /** 00099 * Remove and return the item at the back of the queue. Throw a 00100 * runtime exception if the queue is empty. 00101 * 00102 * @return the item at the tail of the queue 00103 */ 00104 public Object popBack(); 00105 00106 }