    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 * @param <K> the type of keys
    026 * @param <V> the type of mapped values
    027 * @since 3.0
    028 */
    029public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V> implements Map.Entry<K, V> {
    030
    031    /**
    032     * Constructs a new entry with the given key and given value.
    033     *
    034     * @param key  the key for the entry, may be null
    035     * @param value  the value for the entry, may be null
    036     */
    037    protected AbstractMapEntry(final K key, final V value) {
    038        super(key, value);
    039    }
    040
    041    /**
    042     * Compares this {@code Map.Entry} with another {@code Map.Entry}.
    043     * <p>
    044     * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
    045     *
    046     * @param obj  the object to compare to
    047     * @return true if equal key and value
    048     */
    049    @Override
    050    public boolean equals(final Object obj) {
    051        if (obj == this) {
    052            return true;
    053        }
    054        if (!(obj instanceof Map.Entry)) {
    055            return false;
    056        }
    057        final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
    058        return
    059            (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
    060            (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
    061    }
    062
    063    /**
    064     * Gets a hashCode compatible with the equals method.
    065     * <p>
    066     * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
    067     *
    068     * @return a suitable hash code
    069     */
    070    @Override
    071    public int hashCode() {
    072        return (getKey() == null ? 0 : getKey().hashCode()) ^
    073               (getValue() == null ? 0 : getValue().hashCode());
    074    }
    075
    076    /**
    077     * Sets the value stored in this {@code Map.Entry}.
    078     * <p>
    079     * This {@code Map.Entry} is not connected to a Map, so only the
    080     * local data is changed.
    081     *
    082     * @param value  the new value
    083     * @return the previous value
    084     */
    085    @Override
    086    public V setValue(final V value) { // NOPMD
    087        return super.setValue(value);
    088    }
    089
    090}