org.apache.commons.collections.map.CaseInsensitiveMap Maven / Gradle / Ivy

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections.map;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Map;

/**
 * A case-insensitive Map.
 * 
 * Before keys are added to the map or compared to other existing keys, they are converted
 * to all lowercase in a locale-independent fashion by using information from the Unicode
 * data file.
 * 

 * Null keys are supported.  
 * 

 * The keySet() method returns all lowercase keys, or nulls.
 * 

 * Example:
 * 

 *  Map map = new CaseInsensitiveMap();
 *  map.put("One", "One");
 *  map.put("Two", "Two");
 *  map.put(null, "Three");
 *  map.put("one", "Four");
 * 
 * creates a CaseInsensitiveMap with three entries.

 * map.get(null) returns "Three" and map.get("ONE")
 * returns "Four".  The Set returned by keySet()
 * equals {"one", "two", null}.
 * 
 * Note that CaseInsensitiveMap is not synchronized and is not thread-safe.
 * If you wish to use this map from multiple threads concurrently, you must use
 * appropriate synchronization. The simplest approach is to wrap this map
 * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw 
 * exceptions when accessed by concurrent threads without synchronization.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 1713181 $ $Date: 2015-11-07 22:17:00 +0100 (Sat, 07 Nov 2015) $
 *
 * @author Commons-Collections team
 */
public class CaseInsensitiveMap extends AbstractHashedMap implements Serializable, Cloneable {

    /** Serialisation version */
    private static final long serialVersionUID = -7074655917369299456L;

    /**
     * Constructs a new empty map with default size and load factor.
     */
    public CaseInsensitiveMap() {
        super(DEFAULT_CAPACITY, DEFAULT_LOAD_FACTOR, DEFAULT_THRESHOLD);
    }

    /**
     * Constructs a new, empty map with the specified initial capacity. 
     *
     * @param initialCapacity  the initial capacity
     * @throws IllegalArgumentException if the initial capacity is less than one
     */
    public CaseInsensitiveMap(int initialCapacity) {
        super(initialCapacity);
    }

    /**
     * Constructs a new, empty map with the specified initial capacity and
     * load factor. 
     *
     * @param initialCapacity  the initial capacity
     * @param loadFactor  the load factor
     * @throws IllegalArgumentException if the initial capacity is less than one
     * @throws IllegalArgumentException if the load factor is less than zero
     */
    public CaseInsensitiveMap(int initialCapacity, float loadFactor) {
        super(initialCapacity, loadFactor);
    }

    /**
     * Constructor copying elements from another map.
     * 

     * Keys will be converted to lower case strings, which may cause
     * some entries to be removed (if string representation of keys differ
     * only by character case).
     *
     * @param map  the map to copy
     * @throws NullPointerException if the map is null
     */
    public CaseInsensitiveMap(Map map) {
        super(map);
    }

    //-----------------------------------------------------------------------
    /**
     * Overrides convertKey() from {@link AbstractHashedMap} to convert keys to 
     * lower case.
     * 
     * Returns {@link AbstractHashedMap#NULL} if key is null.
     *
     * @param key  the key convert
     * @return the converted key
     */
    protected Object convertKey(Object key) {
        if (key != null) {
            char[] chars = key.toString().toCharArray();
            for (int i = chars.length - 1; i >= 0; i--) {
                chars[i] = Character.toLowerCase(Character.toUpperCase(chars[i]));
            }
            return new String(chars);
        } else {
            return AbstractHashedMap.NULL;
        }
    }   

    //-----------------------------------------------------------------------
    /**
     * Clones the map without cloning the keys or values.
     *
     * @return a shallow clone
     */
    public Object clone() {
        return super.clone();
    }

    /**
     * Write the map out using a custom routine.
     */
    private void writeObject(ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        doWriteObject(out);
    }

    /**
     * Read the map in using a custom routine.
     */
    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        doReadObject(in);
    }
 
}