    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 *      https://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} 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 * <p>
    033 * For instance:
    034 * </p>
    035 * <pre>
    036 * Factory&lt;Date&gt; factory = new Factory&lt;Date&gt;() {
    037 *     public Date create() {
    038 *         return new Date();
    039 *     }
    040 * }
    041 * SortedMap&lt;String, Date&gt; lazy =
    042 *     LazySortedMap.lazySortedMap(new HashMap&lt;String, Date&gt;(), factory);
    043 * Date date = lazy.get("NOW");
    044 * </pre>
    045 *
    046 * <p>
    047 * After the above code is executed, {@code date} will refer to
    048 * a new {@code Date} instance. Furthermore, that {@code Date}
    049 * instance is mapped to the "NOW" key in the map.
    050 * </p>
    051 * <p>
    052 * <strong>Note that LazySortedMap is not synchronized and is not thread-safe.</strong>
    053 * If you wish to use this map from multiple threads concurrently, you must use
    054 * appropriate synchronization. The simplest approach is to wrap this map
    055 * using {@link java.util.Collections#synchronizedSortedMap}. This class may throw
    056 * exceptions when accessed by concurrent threads without synchronization.
    057 * </p>
    058 * <p>
    059 * This class is Serializable from Commons Collections 3.1.
    060 * </p>
    061 *
    062 * @param <K> The type of the keys in this map
    063 * @param <V> The type of the values in this map
    064 * @since 3.0
    065 */
    066public class LazySortedMap<K, V> extends LazyMap<K, V> implements SortedMap<K, V> {
    067
    068    /** Serialization version */
    069    private static final long serialVersionUID = 2715322183617658933L;
    070
    071    /**
    072     * Factory method to create a lazily instantiated sorted map.
    073     *
    074     * @param <K>  the key type
    075     * @param <V>  the value type
    076     * @param map  The map to decorate, must not be null
    077     * @param factory  The factory to use, must not be null
    078     * @return A new lazy sorted map
    079     * @throws NullPointerException if map or factory is null
    080     * @since 4.0
    081     */
    082    public static <K, V> LazySortedMap<K, V> lazySortedMap(final SortedMap<K, V> map,
    083                                                           final Factory<? extends V> factory) {
    084        return new LazySortedMap<>(map, factory);
    085    }
    086
    087    /**
    088     * Factory method to create a lazily instantiated sorted map.
    089     *
    090     * @param <K>  the key type
    091     * @param <V>  the value type
    092     * @param map  The map to decorate, must not be null
    093     * @param factory  The factory to use, must not be null
    094     * @return A new lazy sorted map
    095     * @throws NullPointerException if map or factory is null
    096     * @since 4.0
    097     */
    098    public static <K, V> LazySortedMap<K, V> lazySortedMap(final SortedMap<K, V> map,
    099                                                           final Transformer<? super K, ? extends V> factory) {
    100        return new LazySortedMap<>(map, factory);
    101    }
    102
    103    /**
    104     * Constructor that wraps (not copies).
    105     *
    106     * @param map  The map to decorate, must not be null
    107     * @param factory  The factory to use, must not be null
    108     * @throws NullPointerException if map or factory is null
    109     */
    110    protected LazySortedMap(final SortedMap<K, V> map, final Factory<? extends V> factory) {
    111        super(map, factory);
    112    }
    113
    114    /**
    115     * Constructor that wraps (not copies).
    116     *
    117     * @param map  The map to decorate, must not be null
    118     * @param factory  The factory to use, must not be null
    119     * @throws NullPointerException if map or factory is null
    120     */
    121    protected LazySortedMap(final SortedMap<K, V> map, final Transformer<? super K, ? extends V> factory) {
    122        super(map, factory);
    123    }
    124
    125    @Override
    126    public Comparator<? super K> comparator() {
    127        return getSortedMap().comparator();
    128    }
    129
    130    @Override
    131    public K firstKey() {
    132        return getSortedMap().firstKey();
    133    }
    134
    135    /**
    136     * Gets the map being decorated.
    137     *
    138     * @return The decorated map
    139     */
    140    protected SortedMap<K, V> getSortedMap() {
    141        return (SortedMap<K, V>) map;
    142    }
    143
    144    @Override
    145    public SortedMap<K, V> headMap(final K toKey) {
    146        final SortedMap<K, V> map = getSortedMap().headMap(toKey);
    147        return new LazySortedMap<>(map, factory);
    148    }
    149
    150    @Override
    151    public K lastKey() {
    152        return getSortedMap().lastKey();
    153    }
    154
    155    @Override
    156    public SortedMap<K, V> subMap(final K fromKey, final K toKey) {
    157        final SortedMap<K, V> map = getSortedMap().subMap(fromKey, toKey);
    158        return new LazySortedMap<>(map, factory);
    159    }
    160
    161    @Override
    162    public SortedMap<K, V> tailMap(final K fromKey) {
    163        final SortedMap<K, V> map = getSortedMap().tailMap(fromKey);
    164        return new LazySortedMap<>(map, factory);
    165    }
    166
    167}