    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 *      https://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.Map.Entry;
    021import java.util.Objects;
    022
    023/**
    024 * Abstract Pair class to assist with creating correct
    025 * {@link Entry Map.Entry} implementations.
    026 *
    027 * @param <K> The type of keys
    028 * @param <V> The type of mapped values
    029 * @since 3.0
    030 */
    031public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V> implements Map.Entry<K, V> {
    032
    033    /**
    034     * Constructs a new entry with the given key and given value.
    035     *
    036     * @param key  The key for the entry, may be null
    037     * @param value  The value for the entry, may be null
    038     */
    039    protected AbstractMapEntry(final K key, final V value) {
    040        super(key, value);
    041    }
    042
    043    /**
    044     * Compares this {@code Map.Entry} with another {@code Map.Entry}.
    045     * <p>
    046     * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
    047     *
    048     * @param obj  The object to compare to
    049     * @return true if equal key and value
    050     */
    051    @Override
    052    public boolean equals(final Object obj) {
    053        if (obj == this) {
    054            return true;
    055        }
    056        if (!(obj instanceof Map.Entry)) {
    057            return false;
    058        }
    059        final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
    060        return Objects.equals(getKey(), other.getKey()) &&
    061               Objects.equals(getValue(), other.getValue());
    062    }
    063
    064    /**
    065     * Gets a hashCode compatible with the equals method.
    066     * <p>
    067     * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
    068     *
    069     * @return A suitable hash code
    070     */
    071    @Override
    072    public int hashCode() {
    073        return (getKey() == null ? 0 : getKey().hashCode()) ^
    074               (getValue() == null ? 0 : getValue().hashCode());
    075    }
    076
    077    /**
    078     * Sets the value stored in this {@code Map.Entry}.
    079     * <p>
    080     * This {@code Map.Entry} is not connected to a Map, so only the
    081     * local data is changed.
    082     *
    083     * @param value  The new value
    084     * @return The previous value
    085     */
    086    @Override
    087    public V setValue(final V value) { // NOPMD
    088        return super.setValue(value);
    089    }
    090
    091}