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 * @param <K> the type of keys
026 * @param <V> the type of values
027 * @since 3.0
028 */
029public abstract class AbstractKeyValue<K, V> implements KeyValue<K, V> {
030
031    /** The key */
032    private K key;
033    /** The value */
034    private V value;
035
036    /**
037     * Constructs a new pair with the specified key and given value.
038     *
039     * @param key  the key for the entry, may be null
040     * @param value  the value for the entry, may be null
041     */
042    protected AbstractKeyValue(final K key, final V value) {
043        super();
044        this.key = key;
045        this.value = value;
046    }
047
048    /**
049     * Gets the key from the pair.
050     *
051     * @return the key
052     */
053    @Override
054    public K getKey() {
055        return key;
056    }
057
058    protected K setKey(final K key) {
059        final K old = this.key;
060        this.key = key;
061        return old;
062    }
063
064    /**
065     * Gets the value from the pair.
066     *
067     * @return the value
068     */
069    @Override
070    public V getValue() {
071        return value;
072    }
073
074    protected V setValue(final V value) {
075        final V old = this.value;
076        this.value = value;
077        return old;
078    }
079
080    /**
081     * Gets a debugging String view of the pair.
082     *
083     * @return a String view of the entry
084     */
085    @Override
086    public String toString() {
087        return new StringBuilder()
088            .append(getKey())
089            .append('=')
090            .append(getValue())
091            .toString();
092    }
093
094}