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