    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 */
    017package org.apache.commons.collections4.map;
    018
    019import java.util.Comparator;
    020import java.util.SortedMap;
    021
    022import org.apache.commons.collections4.Factory;
    023import org.apache.commons.collections4.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&lt;Date&gt; factory = new Factory&lt;Date&gt;() {
    035 *     public Date create() {
    036 *         return new Date();
    037 *     }
    038 * }
    039 * SortedMap&lt;String, Date&gt; lazy =
    040 *     LazySortedMap.lazySortedMap(new HashMap&lt;String, Date&gt;(), factory);
    041 * Date date = lazy.get("NOW");
    042 * </pre>
    043 *
    044 * After the above code is executed, <code>date</code> will refer to
    045 * a new <code>Date</code> instance. Furthermore, that <code>Date</code>
    046 * instance is mapped to the "NOW" key in the map.
    047 * <p>
    048 * <strong>Note that LazySortedMap is not synchronized and is not thread-safe.</strong>
    049 * If you wish to use this map from multiple threads concurrently, you must use
    050 * appropriate synchronization. The simplest approach is to wrap this map
    051 * using {@link java.util.Collections#synchronizedSortedMap}. This class may throw
    052 * exceptions when accessed by concurrent threads without synchronization.
    053 * <p>
    054 * This class is Serializable from Commons Collections 3.1.
    055 *
    056 * @param <K> the type of the keys in this map
    057 * @param <V> the type of the values in this map
    058 * @since 3.0
    059 */
    060public class LazySortedMap<K,V> extends LazyMap<K,V> implements SortedMap<K,V> {
    061
    062    /** Serialization version */
    063    private static final long serialVersionUID = 2715322183617658933L;
    064
    065    /**
    066     * Factory method to create a lazily instantiated sorted map.
    067     *
    068     * @param <K>  the key type
    069     * @param <V>  the value type
    070     * @param map  the map to decorate, must not be null
    071     * @param factory  the factory to use, must not be null
    072     * @return a new lazy sorted map
    073     * @throws NullPointerException if map or factory is null
    074     * @since 4.0
    075     */
    076    public static <K, V> LazySortedMap<K, V> lazySortedMap(final SortedMap<K, V> map,
    077                                                           final Factory<? extends V> factory) {
    078        return new LazySortedMap<>(map, factory);
    079    }
    080
    081    /**
    082     * Factory method to create a lazily instantiated sorted map.
    083     *
    084     * @param <K>  the key type
    085     * @param <V>  the value type
    086     * @param map  the map to decorate, must not be null
    087     * @param factory  the factory to use, must not be null
    088     * @return a new lazy sorted map
    089     * @throws NullPointerException if map or factory is null
    090     * @since 4.0
    091     */
    092    public static <K, V> LazySortedMap<K, V> lazySortedMap(final SortedMap<K, V> map,
    093                                                           final Transformer<? super K, ? extends V> factory) {
    094        return new LazySortedMap<>(map, factory);
    095    }
    096
    097    //-----------------------------------------------------------------------
    098    /**
    099     * Constructor that wraps (not copies).
    100     *
    101     * @param map  the map to decorate, must not be null
    102     * @param factory  the factory to use, must not be null
    103     * @throws NullPointerException if map or factory is null
    104     */
    105    protected LazySortedMap(final SortedMap<K,V> map, final Factory<? extends V> factory) {
    106        super(map, factory);
    107    }
    108
    109    /**
    110     * Constructor that wraps (not copies).
    111     *
    112     * @param map  the map to decorate, must not be null
    113     * @param factory  the factory to use, must not be null
    114     * @throws NullPointerException if map or factory is null
    115     */
    116    protected LazySortedMap(final SortedMap<K,V> map, final Transformer<? super K, ? extends V> factory) {
    117        super(map, factory);
    118    }
    119
    120    //-----------------------------------------------------------------------
    121    /**
    122     * Gets the map being decorated.
    123     *
    124     * @return the decorated map
    125     */
    126    protected SortedMap<K,V> getSortedMap() {
    127        return (SortedMap<K,V>) map;
    128    }
    129
    130    //-----------------------------------------------------------------------
    131    @Override
    132    public K firstKey() {
    133        return getSortedMap().firstKey();
    134    }
    135
    136    @Override
    137    public K lastKey() {
    138        return getSortedMap().lastKey();
    139    }
    140
    141    @Override
    142    public Comparator<? super K> comparator() {
    143        return getSortedMap().comparator();
    144    }
    145
    146    @Override
    147    public SortedMap<K,V> subMap(final K fromKey, final K toKey) {
    148        final SortedMap<K,V> map = getSortedMap().subMap(fromKey, toKey);
    149        return new LazySortedMap<>(map, factory);
    150    }
    151
    152    @Override
    153    public SortedMap<K,V> headMap(final K toKey) {
    154        final SortedMap<K,V> map = getSortedMap().headMap(toKey);
    155        return new LazySortedMap<>(map, factory);
    156    }
    157
    158    @Override
    159    public SortedMap<K,V> tailMap(final K fromKey) {
    160        final SortedMap<K,V> map = getSortedMap().tailMap(fromKey);
    161        return new LazySortedMap<>(map, factory);
    162    }
    163
    164}