/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package org.apache.commons.collections4.keyvalue;

import java.util.Map;

/**

 * Abstract Pair class to assist with creating correct

 * {@link java.util.Map.Entry Map.Entry} implementations.

 *

 * @param <K> the type of keys

 * @param <V> the type of mapped values

 * @since 3.0

 */

public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V> implements Map.Entry<K, V> {

    /**

     * Constructs a new entry with the given key and given value.

     *

     * @param key  the key for the entry, may be null

     * @param value  the value for the entry, may be null

     */

    protected AbstractMapEntry(final K key, final V value) {

        super(key, value);

    }

    // Map.Entry interface

    //-------------------------------------------------------------------------

    /**

     * Sets the value stored in this <code>Map.Entry</code>.

     * <p>

     * This <code>Map.Entry</code> is not connected to a Map, so only the

     * local data is changed.

     *

     * @param value  the new value

     * @return the previous value

     */

    @Override

    public V setValue(final V value) { // NOPMD

        return super.setValue(value);

    }

    /**

     * Compares this <code>Map.Entry</code> with another <code>Map.Entry</code>.

     * <p>

     * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}

     *

     * @param obj  the object to compare to

     * @return true if equal key and value

     */

    @Override

    public boolean equals(final Object obj) {

        if (obj == this) {

            return true;

        }

        if (obj instanceof Map.Entry == false) {

            return false;

        }

        final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;

        return

            (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&

            (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));

    }

    /**

     * Gets a hashCode compatible with the equals method.

     * <p>

     * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}

     *

     * @return a suitable hash code

     */

    @Override

    public int hashCode() {

        return (getKey() == null ? 0 : getKey().hashCode()) ^

               (getValue() == null ? 0 : getValue().hashCode());

    }

}