    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 */
    027public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V> implements Map.Entry<K, V> {
    028
    029    /**
    030     * Constructs a new entry with the given key and given value.
    031     *
    032     * @param key  the key for the entry, may be null
    033     * @param value  the value for the entry, may be null
    034     */
    035    protected AbstractMapEntry(final K key, final V value) {
    036        super(key, value);
    037    }
    038
    039    // Map.Entry interface
    040    //-------------------------------------------------------------------------
    041    /**
    042     * Sets the value stored in this <code>Map.Entry</code>.
    043     * <p>
    044     * This <code>Map.Entry</code> is not connected to a Map, so only the
    045     * local data is changed.
    046     *
    047     * @param value  the new value
    048     * @return the previous value
    049     */
    050    @Override
    051    public V setValue(final V value) { // NOPMD
    052        return super.setValue(value);
    053    }
    054
    055    /**
    056     * Compares this <code>Map.Entry</code> with another <code>Map.Entry</code>.
    057     * <p>
    058     * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
    059     *
    060     * @param obj  the object to compare to
    061     * @return true if equal key and value
    062     */
    063    @Override
    064    public boolean equals(final Object obj) {
    065        if (obj == this) {
    066            return true;
    067        }
    068        if (obj instanceof Map.Entry == false) {
    069            return false;
    070        }
    071        final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
    072        return
    073            (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
    074            (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
    075    }
    076
    077    /**
    078     * Gets a hashCode compatible with the equals method.
    079     * <p>
    080     * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
    081     *
    082     * @return a suitable hash code
    083     */
    084    @Override
    085    public int hashCode() {
    086        return (getKey() == null ? 0 : getKey().hashCode()) ^
    087               (getValue() == null ? 0 : getValue().hashCode());
    088    }
    089
    090}