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 org.apache.commons.collections4.KeyValue;
020
021/**
022 * Abstract pair class to assist with creating <code>KeyValue</code>
023 * and {@link java.util.Map.Entry Map.Entry} implementations.
024 *
025 * @since 3.0
026 * @version $Id: AbstractKeyValue.html 972421 2015-11-14 20:00:04Z tn $
027 */
028public abstract class AbstractKeyValue<K, V> implements KeyValue<K, V> {
029
030    /** The key */
031    private K key;
032    /** The value */
033    private V value;
034
035    /**
036     * Constructs a new pair with the specified key and given value.
037     *
038     * @param key  the key for the entry, may be null
039     * @param value  the value for the entry, may be null
040     */
041    protected AbstractKeyValue(final K key, final V value) {
042        super();
043        this.key = key;
044        this.value = value;
045    }
046
047    /**
048     * Gets the key from the pair.
049     *
050     * @return the key
051     */
052    public K getKey() {
053        return key;
054    }
055
056    protected K setKey(K key) {
057        final K old = this.key;
058        this.key = key;
059        return old;
060    }
061
062    /**
063     * Gets the value from the pair.
064     *
065     * @return the value
066     */
067    public V getValue() {
068        return value;
069    }
070
071    protected V setValue(V value) {
072        final V old = this.value;
073        this.value = value;
074        return old;
075    }
076
077    /**
078     * Gets a debugging String view of the pair.
079     *
080     * @return a String view of the entry
081     */
082    @Override
083    public String toString() {
084        return new StringBuilder()
085            .append(getKey())
086            .append('=')
087            .append(getValue())
088            .toString();
089    }
090
091}