    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.lang3.tuple;
    018
    019import java.util.Map;
    020
    021/**
    022 * <p>A mutable pair consisting of two {@code Object} elements.</p>
    023 *
    024 * <p>Not #ThreadSafe#</p>
    025 *
    026 * @param <L> the left element type
    027 * @param <R> the right element type
    028 *
    029 * @since 3.0
    030 */
    031public class MutablePair<L, R> extends Pair<L, R> {
    032
    033    /**
    034     * An empty array.
    035     * <p>
    036     * Consider using {@link #emptyArray()} to avoid generics warnings.
    037     * </p>
    038     *
    039     * @since 3.10.
    040     */
    041    public static final MutablePair<?, ?>[] EMPTY_ARRAY = new MutablePair[0];
    042
    043    /** Serialization version */
    044    private static final long serialVersionUID = 4954918890077093841L;
    045
    046    /**
    047     * Returns the empty array singleton that can be assigned without compiler warning.
    048     *
    049     * @param <L> the left element type
    050     * @param <R> the right element type
    051     * @return the empty array singleton that can be assigned without compiler warning.
    052     *
    053     * @since 3.10.
    054     */
    055    @SuppressWarnings("unchecked")
    056    public static <L, R> MutablePair<L, R>[] emptyArray() {
    057        return (MutablePair<L, R>[]) EMPTY_ARRAY;
    058    }
    059
    060    /**
    061     * <p>Creates a mutable pair of two objects inferring the generic types.</p>
    062     *
    063     * <p>This factory allows the pair to be created using inference to
    064     * obtain the generic types.</p>
    065     *
    066     * @param <L> the left element type
    067     * @param <R> the right element type
    068     * @param left  the left element, may be null
    069     * @param right  the right element, may be null
    070     * @return a pair formed from the two parameters, not null
    071     */
    072    public static <L, R> MutablePair<L, R> of(final L left, final R right) {
    073        return new MutablePair<>(left, right);
    074    }
    075
    076    /**
    077     * <p>Creates a mutable pair from an existing pair.</p>
    078     *
    079     * <p>This factory allows the pair to be created using inference to
    080     * obtain the generic types.</p>
    081     *
    082     * @param <L> the left element type
    083     * @param <R> the right element type
    084     * @param pair the existing pair.
    085     * @return a pair formed from the two parameters, not null
    086     */
    087    public static <L, R> MutablePair<L, R> of(final Map.Entry<L, R> pair) {
    088        final L left;
    089        final R right;
    090        if (pair != null) {
    091            left = pair.getKey();
    092            right = pair.getValue();
    093        } else {
    094            left = null;
    095            right = null;
    096        }
    097        return new MutablePair<>(left, right);
    098    }
    099
    100    /** Left object */
    101    public L left;
    102
    103    /** Right object */
    104    public R right;
    105
    106    /**
    107     * Create a new pair instance of two nulls.
    108     */
    109    public MutablePair() {
    110    }
    111
    112    /**
    113     * Create a new pair instance.
    114     *
    115     * @param left  the left value, may be null
    116     * @param right  the right value, may be null
    117     */
    118    public MutablePair(final L left, final R right) {
    119        this.left = left;
    120        this.right = right;
    121    }
    122
    123    //-----------------------------------------------------------------------
    124    /**
    125     * {@inheritDoc}
    126     */
    127    @Override
    128    public L getLeft() {
    129        return left;
    130    }
    131
    132    /**
    133     * {@inheritDoc}
    134     */
    135    @Override
    136    public R getRight() {
    137        return right;
    138    }
    139
    140    /**
    141     * Sets the left element of the pair.
    142     *
    143     * @param left  the new value of the left element, may be null
    144     */
    145    public void setLeft(final L left) {
    146        this.left = left;
    147    }
    148
    149    /**
    150     * Sets the right element of the pair.
    151     *
    152     * @param right  the new value of the right element, may be null
    153     */
    154    public void setRight(final R right) {
    155        this.right = right;
    156    }
    157
    158    /**
    159     * Sets the {@code Map.Entry} value.
    160     * This sets the right element of the pair.
    161     *
    162     * @param value  the right value to set, not null
    163     * @return the old value for the right element
    164     */
    165    @Override
    166    public R setValue(final R value) {
    167        final R result = getRight();
    168        setRight(value);
    169        return result;
    170    }
    171
    172}