org.apache.commons.collections4.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.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 {@link 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 {@link java.util.Collections#synchronizedMap(Map)}. This class may throw
* exceptions when accessed by concurrent threads without synchronization.
*
*
* @param the type of the keys in this map
* @param the type of the values in this map
* @since 3.0
*/
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 negative
*/
public CaseInsensitiveMap(final 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 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).
*
* @param map the map to copy
* @throws NullPointerException if the map is null
*/
public CaseInsensitiveMap(final 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
*/
@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.
*
* @return a shallow clone
*/
@Override
public CaseInsensitiveMap clone() {
return (CaseInsensitiveMap) super.clone();
}
/**
* 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.
*
* @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);
}
}