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