1 /* 2 * Copyright 2001-2004 The Apache Software Foundation 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 package org.apache.commons.cache.adt; 17 18 /** 19 * An base implementation of {@link Listable}, supporting 20 * singly-linked lists. 21 * 22 * @version $Id: ListableBase.java 155435 2005-02-26 13:17:27Z dirkv $ 23 * @author Rodney Waldhoff 24 */ 25 public class ListableBase implements Listable, Cloneable { 26 27 /** My following sibling. */ 28 protected transient Listable _next = null; 29 30 /** 31 * No arg constructor. 32 * Equivalent to {@link #ListableBase(org.apache.commons.cache.adt.Listable) <tt>ListableBase(null)</tt>}. 33 */ 34 public ListableBase() { 35 } 36 37 /** 38 * Constructor. 39 * @param next the next element in the list. 40 */ 41 public ListableBase(Listable next) { 42 _next = next; 43 } 44 45 public Listable getNext() { 46 return _next; 47 } 48 49 public boolean hasNext() { 50 return (null != _next); 51 } 52 53 public void setNext(Listable next) { 54 _next = next; 55 } 56 57 /** 58 * Throws {@link UnsupportedOperationException}. 59 */ 60 public Listable getPrev() throws UnsupportedOperationException { 61 throw new UnsupportedOperationException(); 62 } 63 64 /** 65 * Throws {@link UnsupportedOperationException}. 66 */ 67 public boolean hasPrev() throws UnsupportedOperationException { 68 throw new UnsupportedOperationException(); 69 } 70 71 /** 72 * Throws {@link UnsupportedOperationException}. 73 */ 74 public void setPrev(Listable prev) throws UnsupportedOperationException { 75 throw new UnsupportedOperationException(); 76 } 77 }