    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.io.IOException;
    020import java.io.ObjectInputStream;
    021import java.io.ObjectOutputStream;
    022import java.io.Serializable;
    023import java.util.Map;
    024
    025/**
    026 * A case-insensitive {@code Map}.
    027 * <p>
    028 * Before keys are added to the map or compared to other existing keys, they are converted
    029 * to all lowercase in a locale-independent fashion by using information from the Unicode
    030 * data file.
    031 * </p>
    032 * <p>
    033 * Null keys are supported.
    034 * </p>
    035 * <p>
    036 * The {@code keySet()} method returns all lowercase keys, or nulls.
    037 * </p>
    038 * <p>
    039 * Example:
    040 * </p>
    041 * <pre><code>
    042 *  Map&lt;String, String&gt; map = new CaseInsensitiveMap&lt;String, String&gt;();
    043 *  map.put("One", "One");
    044 *  map.put("Two", "Two");
    045 *  map.put(null, "Three");
    046 *  map.put("one", "Four");
    047 * </code></pre>
    048 * <p>
    049 * The example above creates a {@code CaseInsensitiveMap} with three entries.
    050 * </p>
    051 * <p>
    052 * {@code map.get(null)} returns {@code "Three"} and {@code map.get("ONE")}
    053 * returns {@code "Four".}  The {@code Set} returned by {@code keySet()}
    054 * equals {@code {"one", "two", null}.}
    055 * </p>
    056 * <p>
    057 * <strong>This map will violate the detail of various Map and map view contracts.</strong>
    058 * As a general rule, don't compare this map to other maps. In particular, you can't
    059 * use decorators like {@link ListOrderedMap} on it, which silently assume that these
    060 * contracts are fulfilled.
    061 * </p>
    062 * <p>
    063 * <strong>Note that CaseInsensitiveMap is not synchronized and is not thread-safe.</strong>
    064 * If you wish to use this map from multiple threads concurrently, you must use
    065 * appropriate synchronization. The simplest approach is to wrap this map
    066 * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
    067 * exceptions when accessed by concurrent threads without synchronization.
    068 * </p>
    069 *
    070 * @param <K> the type of the keys in this map
    071 * @param <V> the type of the values in this map
    072 * @since 3.0
    073 */
    074public class CaseInsensitiveMap<K, V> extends AbstractHashedMap<K, V> implements Serializable, Cloneable {
    075
    076    /** Serialization version */
    077    private static final long serialVersionUID = -7074655917369299456L;
    078
    079    /**
    080     * Constructs a new empty map with default size and load factor.
    081     */
    082    public CaseInsensitiveMap() {
    083        super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
    084    }
    085
    086    /**
    087     * Constructs a new, empty map with the specified initial capacity.
    088     *
    089     * @param initialCapacity  the initial capacity
    090     * @throws IllegalArgumentException if the initial capacity is negative
    091     */
    092    public CaseInsensitiveMap(final int initialCapacity) {
    093        super(initialCapacity);
    094    }
    095
    096    /**
    097     * Constructs a new, empty map with the specified initial capacity and
    098     * load factor.
    099     *
    100     * @param initialCapacity  the initial capacity
    101     * @param loadFactor  the load factor
    102     * @throws IllegalArgumentException if the initial capacity is negative
    103     * @throws IllegalArgumentException if the load factor is less than zero
    104     */
    105    public CaseInsensitiveMap(final int initialCapacity, final float loadFactor) {
    106        super(initialCapacity, loadFactor);
    107    }
    108
    109    /**
    110     * Constructor copying elements from another map.
    111     * <p>
    112     * Keys will be converted to lower case strings, which may cause
    113     * some entries to be removed (if string representation of keys differ
    114     * only by character case).
    115     *
    116     * @param map  the map to copy
    117     * @throws NullPointerException if the map is null
    118     */
    119    public CaseInsensitiveMap(final Map<? extends K, ? extends V> map) {
    120        super(map);
    121    }
    122
    123    /**
    124     * Clones the map without cloning the keys or values.
    125     *
    126     * @return a shallow clone
    127     */
    128    @Override
    129    public CaseInsensitiveMap<K, V> clone() {
    130        return (CaseInsensitiveMap<K, V>) super.clone();
    131    }
    132
    133    /**
    134     * Overrides convertKey() from {@link AbstractHashedMap} to convert keys to
    135     * lower case.
    136     * <p>
    137     * Returns {@link AbstractHashedMap#NULL} if key is null.
    138     *
    139     * @param key  the key convert
    140     * @return the converted key
    141     */
    142    @Override
    143    protected Object convertKey(final Object key) {
    144        if (key != null) {
    145            final char[] chars = key.toString().toCharArray();
    146            for (int i = chars.length - 1; i >= 0; i--) {
    147                chars[i] = Character.toLowerCase(Character.toUpperCase(chars[i]));
    148            }
    149            return new String(chars);
    150        }
    151        return NULL;
    152    }
    153
    154    /**
    155     * Deserializes the map in using a custom routine.
    156     *
    157     * @param in the input stream
    158     * @throws IOException if an error occurs while reading from the stream
    159     * @throws ClassNotFoundException if an object read from the stream cannot be loaded
    160     */
    161    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    162        in.defaultReadObject();
    163        doReadObject(in);
    164    }
    165
    166    /**
    167     * Serializes this object to an ObjectOutputStream.
    168     *
    169     * @param out the target ObjectOutputStream.
    170     * @throws IOException thrown when an I/O errors occur writing to the target stream.
    171     */
    172    private void writeObject(final ObjectOutputStream out) throws IOException {
    173        out.defaultWriteObject();
    174        doWriteObject(out);
    175    }
    176
    177}