001 /* 002 * Copyright 2001-2004 The Apache Software Foundation 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 package org.apache.commons.cache.adt; 017 018 /** 019 * An base implementation of {@link Listable}, supporting 020 * doubly-linked lists. 021 * 022 * @version $Id: WListableBase.java 155435 2005-02-26 13:17:27Z dirkv $ 023 * @author Rodney Waldhoff 024 */ 025 public class WListableBase extends ListableBase implements Listable, Cloneable { 026 027 /** My preceeding sibling. */ 028 protected transient Listable _prev = null; 029 030 /** 031 * No arg constructor. 032 * Equivalent to {@link #WListableBase(Listable,Listable) <tt>WListableBase(null,null)</tt>}. 033 */ 034 public WListableBase() { 035 } 036 037 /** 038 * Constructor. 039 * @param prev the prev element in the list. 040 * @param next the next element in the list. 041 */ 042 public WListableBase(Listable prev, Listable next) { 043 super(next); 044 _prev = prev; 045 } 046 047 public Listable getPrev() { 048 return _prev; 049 } 050 051 public boolean hasPrev() { 052 return (null != _prev); 053 } 054 055 public void setPrev(Listable prev) { 056 _prev = prev; 057 } 058 }