org.apache.commons.collections15.bidimap.DualHashBidiMap.java Source code

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Here is the source code for org.apache.commons.collections15.bidimap.DualHashBidiMap.java

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// GenericsNote: Converted.
/*
 *  Copyright 2003-2004 The Apache Software Foundation
 *
 *  Licensed 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.collections15.bidimap;

import org.apache.commons.collections15.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;

/**
 * Implementation of <code>BidiMap</code> that uses two <code>HashMap</code> instances.
 * <p/>
 * Two <code>HashMap</code> 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 <code>BidiMap</code> interface.
 * <p/>
 * NOTE: From Commons Collections 3.1, all subclasses will use <code>HashMap</code>
 * and the flawed <code>createMap</code> method is ignored.
 *
 * @author Matthew Hawthorne
 * @author Matt Hall, John Watkinson, Stephen Colebourne
 * @version $Id: DualHashBidiMap.java,v 1.1 2005/10/11 17:05:19 pents90 Exp $
 * @since Commons Collections 3.0
 */
public class DualHashBidiMap<K, V> extends AbstractDualBidiMap<K, V> implements Serializable {

    /**
     * Ensure serialization compatibility
     */
    private static final long serialVersionUID = 721969328361808L;

    /**
     * Creates an empty <code>HashBidiMap</code>.
     */
    public DualHashBidiMap() {
        super(new HashMap<K, V>(), new HashMap<V, K>());
    }

    /**
     * Constructs a <code>HashBidiMap</code> and copies the mappings from
     * specified <code>Map</code>.
     *
     * @param map the map whose mappings are to be placed in this map
     */
    public DualHashBidiMap(Map<? extends K, ? extends V> map) {
        super(new HashMap<K, V>(), new HashMap<V, K>());
        putAll(map);
    }

    /**
     * Constructs a <code>HashBidiMap</code> that decorates the specified maps.
     *
     * @param normalMap      the normal direction map
     * @param reverseMap     the reverse direction map
     * @param inverseBidiMap the inverse BidiMap
     */
    protected DualHashBidiMap(Map<K, V> normalMap, Map<V, K> reverseMap, BidiMap<V, K> 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
     */
    protected <K, V> BidiMap<K, V> createBidiMap(Map<K, V> normalMap, Map<V, K> reverseMap,
            BidiMap<V, K> inverseBidiMap) {
        return new DualHashBidiMap<K, V>(normalMap, reverseMap, inverseBidiMap);
    }

    // Serialization
    //-----------------------------------------------------------------------
    private void writeObject(ObjectOutputStream out) throws IOException {
        out.defaultWriteObject();
        out.writeObject(forwardMap);
    }

    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
        in.defaultReadObject();
        forwardMap = new HashMap<K, V>();
        inverseMap = new HashMap<V, K>();
        Map<K, V> map = (Map<K, V>) in.readObject();
        putAll(map);
    }

}