    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;
    020import java.util.Objects;
    021
    022/**
    023 * Abstract Pair class to assist with creating correct
    024 * {@link java.util.Map.Entry Map.Entry} implementations.
    025 *
    026 * @param <K> the type of keys
    027 * @param <V> the type of mapped values
    028 * @since 3.0
    029 */
    030public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V> implements Map.Entry<K, V> {
    031
    032    /**
    033     * Constructs a new entry with the given key and given value.
    034     *
    035     * @param key  the key for the entry, may be null
    036     * @param value  the value for the entry, may be null
    037     */
    038    protected AbstractMapEntry(final K key, final V value) {
    039        super(key, value);
    040    }
    041
    042    /**
    043     * Compares this {@code Map.Entry} with another {@code Map.Entry}.
    044     * <p>
    045     * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
    046     *
    047     * @param obj  the object to compare to
    048     * @return true if equal key and value
    049     */
    050    @Override
    051    public boolean equals(final Object obj) {
    052        if (obj == this) {
    053            return true;
    054        }
    055        if (!(obj instanceof Map.Entry)) {
    056            return false;
    057        }
    058        final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
    059        return Objects.equals(getKey(), other.getKey()) &&
    060               Objects.equals(getValue(), 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}