    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 *      https://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;
    020import java.util.Objects;
    021
    022/**
    023 * A mutable pair consisting of two {@link Object} elements.
    024 *
    025 * <p>Not #ThreadSafe#</p>
    026 *
    027 * @param <L> the left element type.
    028 * @param <R> the right element type.
    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 = {};
    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     * @since 3.10
    053     */
    054    @SuppressWarnings("unchecked")
    055    public static <L, R> MutablePair<L, R>[] emptyArray() {
    056        return (MutablePair<L, R>[]) EMPTY_ARRAY;
    057    }
    058
    059    /**
    060     * Creates a mutable pair of two objects inferring the generic types.
    061     *
    062     * @param <L> the left element type.
    063     * @param <R> the right element type.
    064     * @param left  the left element, may be null.
    065     * @param right  the right element, may be null.
    066     * @return a mutable pair formed from the two parameters, not null.
    067     */
    068    public static <L, R> MutablePair<L, R> of(final L left, final R right) {
    069        return new MutablePair<>(left, right);
    070    }
    071
    072    /**
    073     * Creates a mutable pair from a map entry.
    074     *
    075     * @param <L> the left element type.
    076     * @param <R> the right element type.
    077     * @param pair the existing map entry.
    078     * @return a mutable pair formed from the map entry.
    079     */
    080    public static <L, R> MutablePair<L, R> of(final Map.Entry<L, R> pair) {
    081        final L left;
    082        final R right;
    083        if (pair != null) {
    084            left = pair.getKey();
    085            right = pair.getValue();
    086        } else {
    087            left = null;
    088            right = null;
    089        }
    090        return new MutablePair<>(left, right);
    091    }
    092
    093    /**
    094     * Creates a mutable pair of two non-null objects inferring the generic types.
    095     *
    096     * @param <L> the left element type.
    097     * @param <R> the right element type.
    098     * @param left  the left element, may not be null.
    099     * @param right  the right element, may not be null.
    100     * @return a mutable pair formed from the two parameters, not null.
    101     * @throws NullPointerException if any input is null.
    102     * @since 3.13.0
    103     */
    104    public static <L, R> MutablePair<L, R> ofNonNull(final L left, final R right) {
    105        return of(Objects.requireNonNull(left, "left"), Objects.requireNonNull(right, "right"));
    106    }
    107
    108    /**
    109     * Creates a mutable pair from a map entry.
    110     *
    111     * @param <L> the left element type
    112     * @param <R> the right element type
    113     * @param pair the existing map entry.
    114     * @return a mutable pair formed from the map entry
    115     * @throws NullPointerException if the pair is null.
    116     * @since 3.20
    117     */
    118    public static <L, R> MutablePair<L, R> ofNonNull(final Map.Entry<L, R> pair) {
    119        return of(Objects.requireNonNull(pair, "pair"));
    120    }
    121
    122    /** Left object. */
    123    public L left;
    124
    125    /** Right object. */
    126    public R right;
    127
    128    /**
    129     * Create a new pair instance of two nulls.
    130     */
    131    public MutablePair() {
    132    }
    133
    134    /**
    135     * Create a new pair instance.
    136     *
    137     * @param left  the left value, may be null.
    138     * @param right  the right value, may be null.
    139     */
    140    public MutablePair(final L left, final R right) {
    141        this.left = left;
    142        this.right = right;
    143    }
    144
    145    /**
    146     * {@inheritDoc}
    147     */
    148    @Override
    149    public L getLeft() {
    150        return left;
    151    }
    152
    153    /**
    154     * {@inheritDoc}
    155     */
    156    @Override
    157    public R getRight() {
    158        return right;
    159    }
    160
    161    /**
    162     * Sets the left element of the pair.
    163     *
    164     * @param left  the new value of the left element, may be null.
    165     */
    166    public void setLeft(final L left) {
    167        this.left = left;
    168    }
    169
    170    /**
    171     * Sets the right element of the pair.
    172     *
    173     * @param right  the new value of the right element, may be null.
    174     */
    175    public void setRight(final R right) {
    176        this.right = right;
    177    }
    178
    179    /**
    180     * Sets the {@code Map.Entry} value.
    181     * This sets the right element of the pair.
    182     *
    183     * @param value  the right value to set, not null.
    184     * @return the old value for the right element.
    185     */
    186    @Override
    187    public R setValue(final R value) {
    188        final R result = getRight();
    189        setRight(value);
    190        return result;
    191    }
    192
    193}