001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.collections.map; 018 019 import java.util.Comparator; 020 import java.util.SortedMap; 021 022 import org.apache.commons.collections.Factory; 023 import org.apache.commons.collections.Transformer; 024 025 /** 026 * Decorates another <code>SortedMap</code> to create objects in the map on demand. 027 * <p> 028 * When the {@link #get(Object)} method is called with a key that does not 029 * exist in the map, the factory is used to create the object. The created 030 * object will be added to the map using the requested key. 031 * <p> 032 * For instance: 033 * <pre> 034 * Factory factory = new Factory() { 035 * public Object create() { 036 * return new Date(); 037 * } 038 * } 039 * SortedMap lazy = Lazy.sortedMap(new HashMap(), factory); 040 * Object obj = lazy.get("NOW"); 041 * </pre> 042 * 043 * After the above code is executed, <code>obj</code> will contain 044 * a new <code>Date</code> instance. Furthermore, that <code>Date</code> 045 * instance is mapped to the "NOW" key in the map. 046 * <p> 047 * <strong>Note that LazySortedMap is not synchronized and is not thread-safe.</strong> 048 * If you wish to use this map from multiple threads concurrently, you must use 049 * appropriate synchronization. The simplest approach is to wrap this map 050 * using {@link java.util.Collections#synchronizedSortedMap}. This class may throw 051 * exceptions when accessed by concurrent threads without synchronization. 052 * <p> 053 * This class is Serializable from Commons Collections 3.1. 054 * 055 * @since Commons Collections 3.0 056 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 057 * 058 * @author Stephen Colebourne 059 * @author Paul Jack 060 */ 061 public class LazySortedMap 062 extends LazyMap 063 implements SortedMap { 064 065 /** Serialization version */ 066 private static final long serialVersionUID = 2715322183617658933L; 067 068 /** 069 * Factory method to create a lazily instantiated sorted map. 070 * 071 * @param map the map to decorate, must not be null 072 * @param factory the factory to use, must not be null 073 * @throws IllegalArgumentException if map or factory is null 074 */ 075 public static SortedMap decorate(SortedMap map, Factory factory) { 076 return new LazySortedMap(map, factory); 077 } 078 079 /** 080 * Factory method to create a lazily instantiated sorted map. 081 * 082 * @param map the map to decorate, must not be null 083 * @param factory the factory to use, must not be null 084 * @throws IllegalArgumentException if map or factory is null 085 */ 086 public static SortedMap decorate(SortedMap map, Transformer factory) { 087 return new LazySortedMap(map, factory); 088 } 089 090 //----------------------------------------------------------------------- 091 /** 092 * Constructor that wraps (not copies). 093 * 094 * @param map the map to decorate, must not be null 095 * @param factory the factory to use, must not be null 096 * @throws IllegalArgumentException if map or factory is null 097 */ 098 protected LazySortedMap(SortedMap map, Factory factory) { 099 super(map, factory); 100 } 101 102 /** 103 * Constructor that wraps (not copies). 104 * 105 * @param map the map to decorate, must not be null 106 * @param factory the factory to use, must not be null 107 * @throws IllegalArgumentException if map or factory is null 108 */ 109 protected LazySortedMap(SortedMap map, Transformer factory) { 110 super(map, factory); 111 } 112 113 //----------------------------------------------------------------------- 114 /** 115 * Gets the map being decorated. 116 * 117 * @return the decorated map 118 */ 119 protected SortedMap getSortedMap() { 120 return (SortedMap) map; 121 } 122 123 //----------------------------------------------------------------------- 124 public Object firstKey() { 125 return getSortedMap().firstKey(); 126 } 127 128 public Object lastKey() { 129 return getSortedMap().lastKey(); 130 } 131 132 public Comparator comparator() { 133 return getSortedMap().comparator(); 134 } 135 136 public SortedMap subMap(Object fromKey, Object toKey) { 137 SortedMap map = getSortedMap().subMap(fromKey, toKey); 138 return new LazySortedMap(map, factory); 139 } 140 141 public SortedMap headMap(Object toKey) { 142 SortedMap map = getSortedMap().headMap(toKey); 143 return new LazySortedMap(map, factory); 144 } 145 146 public SortedMap tailMap(Object fromKey) { 147 SortedMap map = getSortedMap().tailMap(fromKey); 148 return new LazySortedMap(map, factory); 149 } 150 151 }