org.apache.commons.collections4.bidimap.DualHashBidiMap Maven / Gradle / Ivy
Show all versions of commons-collections4 Show documentation
/*
* 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.bidimap;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import org.apache.commons.collections4.BidiMap;
/**
* Implementation of {@link BidiMap} that uses two {@link HashMap} instances.
*
* Two {@link HashMap} instances are used in this class.
* This provides fast lookups at the expense of storing two sets of map entries.
* Commons Collections would welcome the addition of a direct hash-based
* implementation of the {@link BidiMap} interface.
*
* NOTE: From Commons Collections 3.1, all subclasses will use {@link HashMap}
* and the flawed createMap method is ignored.
*
* @param the type of the keys in the map
* @param the type of the values in the map
*
* @since 3.0
*/
public class DualHashBidiMap extends AbstractDualBidiMap implements Serializable {
/** Ensure serialization compatibility */
private static final long serialVersionUID = 721969328361808L;
/**
* Creates an empty HashBidiMap.
*/
public DualHashBidiMap() {
super(new HashMap(), new HashMap());
}
/**
* Constructs a HashBidiMap and copies the mappings from
* specified Map.
*
* @param map the map whose mappings are to be placed in this map
*/
public DualHashBidiMap(final Map map) {
super(new HashMap(), new HashMap());
putAll(map);
}
/**
* Constructs a HashBidiMap that decorates the specified maps.
*
* @param normalMap the normal direction map
* @param reverseMap the reverse direction map
* @param inverseBidiMap the inverse BidiMap
*/
protected DualHashBidiMap(final Map normalMap, final Map reverseMap,
final BidiMap inverseBidiMap) {
super(normalMap, reverseMap, inverseBidiMap);
}
/**
* Creates a new instance of this object.
*
* @param normalMap the normal direction map
* @param reverseMap the reverse direction map
* @param inverseBidiMap the inverse BidiMap
* @return new bidi map
*/
@Override
protected BidiMap createBidiMap(final Map normalMap, final Map reverseMap,
final BidiMap inverseBidiMap) {
return new DualHashBidiMap<>(normalMap, reverseMap, inverseBidiMap);
}
// Serialization
//-----------------------------------------------------------------------
private void writeObject(final ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeObject(normalMap);
}
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
normalMap = new HashMap<>();
reverseMap = new HashMap<>();
@SuppressWarnings("unchecked") // will fail at runtime if stream is incorrect
final Map map = (Map) in.readObject();
putAll(map);
}
}