001: package com.quadcap.util.collections;
002:
003: /* Copyright 1997 - 2003 Quadcap Software. All rights reserved.
004: *
005: * This software is distributed under the Quadcap Free Software License.
006: * This software may be used or modified for any purpose, personal or
007: * commercial. Open Source redistributions are permitted. Commercial
008: * redistribution of larger works derived from, or works which bundle
009: * this software requires a "Commercial Redistribution License"; see
010: * http://www.quadcap.com/purchase.
011: *
012: * Redistributions qualify as "Open Source" under one of the following terms:
013: *
014: * Redistributions are made at no charge beyond the reasonable cost of
015: * materials and delivery.
016: *
017: * Redistributions are accompanied by a copy of the Source Code or by an
018: * irrevocable offer to provide a copy of the Source Code for up to three
019: * years at the cost of materials and delivery. Such redistributions
020: * must allow further use, modification, and redistribution of the Source
021: * Code under substantially the same terms as this license.
022: *
023: * Redistributions of source code must retain the copyright notices as they
024: * appear in each source code file, these license terms, and the
025: * disclaimer/limitation of liability set forth as paragraph 6 below.
026: *
027: * Redistributions in binary form must reproduce this Copyright Notice,
028: * these license terms, and the disclaimer/limitation of liability set
029: * forth as paragraph 6 below, in the documentation and/or other materials
030: * provided with the distribution.
031: *
032: * The Software is provided on an "AS IS" basis. No warranty is
033: * provided that the Software is free of defects, or fit for a
034: * particular purpose.
035: *
036: * Limitation of Liability. Quadcap Software shall not be liable
037: * for any damages suffered by the Licensee or any third party resulting
038: * from use of the Software.
039: */
040:
041: /**
042: * This class implements a queue with a capacity.
043: *
044: * @author Stan Bailes
045: */
046: public interface Queue {
047: /**
048: * Specify the maximum capacity of this queue, -1 means unbounded.
049: *
050: * @param capacity the new capacity of the queue, or -1 to specify a
051: * queue of unlimited size.
052: */
053: public void setCapacity(int capacity);
054:
055: /**
056: * Return the number of items in the queue.
057: * @return the queue's size
058: */
059: public int size();
060:
061: /**
062: * Add an object to the front of the queue.
063: *
064: * @param obj the object to add
065: */
066: public void addFront(Object obj);
067:
068: /**
069: * Add an object to the back of the queue.
070: * @param obj the object to add
071: */
072: public void addBack(Object obj);
073:
074: /**
075: * Access the object at the front of the queue. Throw a runtime exception
076: * if the queue is empty.
077: *
078: * @return the item at the head of the queue
079: */
080: public Object head();
081:
082: /**
083: * Access the object at the back of the queue. Throw a runtime exception
084: * if the queue is empty.
085: *
086: * @return the item at the tail of the queue
087: */
088: public Object tail();
089:
090: /**
091: * Remove and return the item at the front of the queue. Throw a
092: * runtime exception if the queue is empty.
093: *
094: * @return the item at the head of the queue
095: */
096: public Object popFront();
097:
098: /**
099: * Remove and return the item at the back of the queue. Throw a
100: * runtime exception if the queue is empty.
101: *
102: * @return the item at the tail of the queue
103: */
104: public Object popBack();
105:
106: }
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