001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.keyvalue;
018
019import java.util.Map;
020
021/**
022 * Abstract Pair class to assist with creating correct
023 * {@link java.util.Map.Entry Map.Entry} implementations.
024 *
025 * @since 3.0
026 * @version $Id: AbstractMapEntry.html 972421 2015-11-14 20:00:04Z tn $
027 */
028public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V> implements Map.Entry<K, V> {
029
030    /**
031     * Constructs a new entry with the given key and given value.
032     *
033     * @param key  the key for the entry, may be null
034     * @param value  the value for the entry, may be null
035     */
036    protected AbstractMapEntry(final K key, final V value) {
037        super(key, value);
038    }
039
040    // Map.Entry interface
041    //-------------------------------------------------------------------------
042    /**
043     * Sets the value stored in this <code>Map.Entry</code>.
044     * <p>
045     * This <code>Map.Entry</code> is not connected to a Map, so only the
046     * local data is changed.
047     *
048     * @param value  the new value
049     * @return the previous value
050     */
051    @Override
052    public V setValue(final V value) {
053        return super.setValue(value);
054    }
055
056    /**
057     * Compares this <code>Map.Entry</code> with another <code>Map.Entry</code>.
058     * <p>
059     * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
060     *
061     * @param obj  the object to compare to
062     * @return true if equal key and value
063     */
064    @Override
065    public boolean equals(final Object obj) {
066        if (obj == this) {
067            return true;
068        }
069        if (obj instanceof Map.Entry == false) {
070            return false;
071        }
072        final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
073        return
074            (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
075            (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
076    }
077
078    /**
079     * Gets a hashCode compatible with the equals method.
080     * <p>
081     * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
082     *
083     * @return a suitable hash code
084     */
085    @Override
086    public int hashCode() {
087        return (getKey() == null ? 0 : getKey().hashCode()) ^
088               (getValue() == null ? 0 : getValue().hashCode());
089    }
090
091}