    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}
    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        this.key = key;
    044        this.value = value;
    045    }
    046
    047    /**
    048     * Gets the key from the pair.
    049     *
    050     * @return the key
    051     */
    052    @Override
    053    public K getKey() {
    054        return key;
    055    }
    056
    057    /**
    058     * Gets the value from the pair.
    059     *
    060     * @return the value
    061     */
    062    @Override
    063    public V getValue() {
    064        return value;
    065    }
    066
    067    /**
    068     * Sets the key.
    069     *
    070     * @param key The key.
    071     * @return The previous key.
    072     */
    073    protected K setKey(final K key) {
    074        final K old = this.key;
    075        this.key = key;
    076        return old;
    077    }
    078
    079    /**
    080     * Sets the value.
    081     *
    082     * @param value The value.
    083     * @return The previous value.
    084     */
    085    protected V setValue(final V value) {
    086        final V old = this.value;
    087        this.value = value;
    088        return old;
    089    }
    090
    091    /**
    092     * Gets a debugging String view of the pair.
    093     *
    094     * @return a String view of the entry
    095     */
    096    @Override
    097    public String toString() {
    098        return new StringBuilder()
    099            .append(getKey())
    100            .append('=')
    101            .append(getValue())
    102            .toString();
    103    }
    104
    105}