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 * 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.
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package org.apache.commons.collections4.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<String, String> map = new CaseInsensitiveMap<String, String>();
 map.put("One", "One");
 map.put("Two", "Two");
 map.put(null, "Three");
 map.put("one", "Four");


The example above 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}.


This map will violate the detail of various Map and map view contracts. As a general rule, don't compare this map to other maps. In particular, you can't use decorators like ListOrderedMap on it, which silently assume that these contracts are fulfilled. 

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 Collections.synchronizedMap(Map<Object,Object>). This class may throw exceptions when accessed by concurrent threads without synchronization. 
Type parameters:
<K> – the type of the keys in this map
<V> – the type of the values in this map
Since:
3.0/**
 * A case-insensitive <code>Map</code>.
 * <p>
 * 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.
 * </p>
 * <p>
 * Null keys are supported.
 * </p>
 * <p>
 * The <code>keySet()</code> method returns all lowercase keys, or nulls.
 * </p>
 * <p>
 * Example:
 * </p>
 * <pre><code>
 *  Map&lt;String, String&gt; map = new CaseInsensitiveMap&lt;String, String&gt;();
 *  map.put("One", "One");
 *  map.put("Two", "Two");
 *  map.put(null, "Three");
 *  map.put("one", "Four");
 * </code></pre>
 * <p>
 * The example above creates a <code>CaseInsensitiveMap</code> with three entries.
 * </p>
 * <p>
 * <code>map.get(null)</code> returns <code>"Three"</code> and <code>map.get("ONE")</code>
 * returns <code>"Four".</code>  The <code>Set</code> returned by <code>keySet()</code>
 * equals <code>{"one", "two", null}.</code>
 * </p>
 * <p>
 * <strong>This map will violate the detail of various Map and map view contracts.</strong>
 * As a general rule, don't compare this map to other maps. In particular, you can't
 * use decorators like {@link ListOrderedMap} on it, which silently assume that these
 * contracts are fulfilled.
 * </p>
 * <p>
 * <strong>Note that CaseInsensitiveMap is not synchronized and is not thread-safe.</strong>
 * 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.
 * </p>
 *
 * @param <K> the type of the keys in this map
 * @param <V> the type of the values in this map
 * @since 3.0
 */
public class CaseInsensitiveMap<K, V> extends AbstractHashedMap<K, V> implements Serializable, Cloneable {

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

    
Constructs a new empty map with default size and load factor.
/**
     * 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.
Params:
initialCapacity –  the initial capacity
Throws:
IllegalArgumentException – if the initial capacity is negative/**
     * Constructs a new, empty map with the specified initial capacity.
     *
     * @param initialCapacity  the initial capacity
     * @throws IllegalArgumentException if the initial capacity is negative
     */
    public CaseInsensitiveMap(final int initialCapacity) {
        super(initialCapacity);
    }

    
Constructs a new, empty map with the specified initial capacity and
load factor.
Params:
initialCapacity –  the initial capacity
loadFactor –  the load factor
Throws:
IllegalArgumentException – if the initial capacity is negative
IllegalArgumentException – if the load factor is less than zero/**
     * 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 negative
     * @throws IllegalArgumentException if the load factor is less than zero
     */
    public CaseInsensitiveMap(final int initialCapacity, final 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).
Params:
map –  the map to copy
Throws:
NullPointerException – if the map is null/**
     * Constructor copying elements from another map.
     * <p>
     * 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(final Map<? extends K, ? extends V> map) {
        super(map);
    }

    //-----------------------------------------------------------------------
    
Overrides convertKey() from AbstractHashedMap to convert keys to lower case. 
 Returns AbstractHashedMap.NULL if key is null. 
Params:
key –  the key convert
Returns:
the converted key/**
     * Overrides convertKey() from {@link AbstractHashedMap} to convert keys to
     * lower case.
     * <p>
     * Returns {@link AbstractHashedMap#NULL} if key is null.
     *
     * @param key  the key convert
     * @return the converted key
     */
    @Override
    protected Object convertKey(final Object key) {
        if (key != null) {
            final 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);
        }
        return AbstractHashedMap.NULL;
    }

    //-----------------------------------------------------------------------
    
Clones the map without cloning the keys or values.
Returns:
a shallow clone/**
     * Clones the map without cloning the keys or values.
     *
     * @return a shallow clone
     */
    @Override
    public CaseInsensitiveMap<K, V> clone() {
        return (CaseInsensitiveMap<K, V>) super.clone();
    }

    
Write the map out using a custom routine.
Params:
out –  the output stream
Throws:
IOException – if an error occurs while writing to the stream/**
     * Write the map out using a custom routine.
     *
     * @param out  the output stream
     * @throws IOException if an error occurs while writing to the stream
     */
    private void writeObject(final ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        doWriteObject(out);
    }

    
Read the map in using a custom routine.
Params:
in – the input stream
Throws:
IOException – if an error occurs while reading from the stream
ClassNotFoundException – if an object read from the stream can not be loaded/**
     * Read the map in using a custom routine.
     *
     * @param in the input stream
     * @throws IOException if an error occurs while reading from the stream
     * @throws ClassNotFoundException if an object read from the stream can not be loaded
     */
    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        doReadObject(in);
    }

}