    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.Objects;
    020
    021/**
    022 * An immutable triple consisting of three {@link Object} elements.
    023 *
    024 * <p>Although the implementation is immutable, there is no restriction on the objects
    025 * that may be stored. If mutable objects are stored in the triple, then the triple
    026 * itself effectively becomes mutable.</p>
    027 *
    028 * <p>#ThreadSafe# if all three objects are thread-safe</p>
    029 *
    030 * @param <L> the left element type
    031 * @param <M> the middle element type
    032 * @param <R> the right element type
    033 *
    034 * @since 3.2
    035 */
    036public class ImmutableTriple<L, M, R> extends Triple<L, M, R> {
    037
    038    /**
    039     * An empty array.
    040     * <p>
    041     * Consider using {@link #emptyArray()} to avoid generics warnings.
    042     * </p>
    043     *
    044     * @since 3.10.
    045     */
    046    public static final ImmutableTriple<?, ?, ?>[] EMPTY_ARRAY = {};
    047
    048    /**
    049     * An immutable triple of nulls.
    050     */
    051    // This is not defined with generics to avoid warnings in call sites.
    052    @SuppressWarnings("rawtypes")
    053    private static final ImmutableTriple NULL = new ImmutableTriple<>(null, null, null);
    054
    055    /** Serialization version */
    056    private static final long serialVersionUID = 1L;
    057
    058    /**
    059     * Returns the empty array singleton that can be assigned without compiler warning.
    060     *
    061     * @param <L> the left element type
    062     * @param <M> the middle element type
    063     * @param <R> the right element type
    064     * @return the empty array singleton that can be assigned without compiler warning.
    065     *
    066     * @since 3.10.
    067     */
    068    @SuppressWarnings("unchecked")
    069    public static <L, M, R> ImmutableTriple<L, M, R>[] emptyArray() {
    070        return (ImmutableTriple<L, M, R>[]) EMPTY_ARRAY;
    071    }
    072
    073    /**
    074     * Returns an immutable triple of nulls.
    075     *
    076     * @param <L> the left element of this triple. Value is {@code null}.
    077     * @param <M> the middle element of this triple. Value is {@code null}.
    078     * @param <R> the right element of this triple. Value is {@code null}.
    079     * @return an immutable triple of nulls.
    080     * @since 3.6
    081     */
    082    @SuppressWarnings("unchecked")
    083    public static <L, M, R> ImmutableTriple<L, M, R> nullTriple() {
    084        return NULL;
    085    }
    086
    087    /**
    088     * Obtains an immutable triple of three objects inferring the generic types.
    089     *
    090     * <p>This factory allows the triple to be created using inference to
    091     * obtain the generic types.</p>
    092     *
    093     * @param <L> the left element type
    094     * @param <M> the middle element type
    095     * @param <R> the right element type
    096     * @param left  the left element, may be null
    097     * @param middle  the middle element, may be null
    098     * @param right  the right element, may be null
    099     * @return a triple formed from the three parameters, not null
    100     */
    101    public static <L, M, R> ImmutableTriple<L, M, R> of(final L left, final M middle, final R right) {
    102        return left != null | middle != null || right != null ? new ImmutableTriple<>(left, middle, right) : nullTriple();
    103    }
    104
    105    /**
    106     * Obtains an immutable triple of three non-null objects inferring the generic types.
    107     *
    108     * <p>This factory allows the triple to be created using inference to
    109     * obtain the generic types.</p>
    110     *
    111     * @param <L> the left element type
    112     * @param <M> the middle element type
    113     * @param <R> the right element type
    114     * @param left  the left element, may not be null
    115     * @param middle  the middle element, may not be null
    116     * @param right  the right element, may not be null
    117     * @return a triple formed from the three parameters, not null
    118     * @throws NullPointerException if any input is null
    119     * @since 3.13.0
    120     */
    121    public static <L, M, R> ImmutableTriple<L, M, R> ofNonNull(final L left, final M middle, final R right) {
    122        return of(Objects.requireNonNull(left, "left"), Objects.requireNonNull(middle, "middle"), Objects.requireNonNull(right, "right"));
    123    }
    124
    125    /** Left object */
    126    public final L left;
    127    /** Middle object */
    128    public final M middle;
    129
    130    /** Right object */
    131    public final R right;
    132
    133    /**
    134     * Create a new triple instance.
    135     *
    136     * @param left  the left value, may be null
    137     * @param middle the middle value, may be null
    138     * @param right  the right value, may be null
    139     */
    140    public ImmutableTriple(final L left, final M middle, final R right) {
    141        this.left = left;
    142        this.middle = middle;
    143        this.right = right;
    144    }
    145
    146    /**
    147     * {@inheritDoc}
    148     */
    149    @Override
    150    public L getLeft() {
    151        return left;
    152    }
    153
    154    /**
    155     * {@inheritDoc}
    156     */
    157    @Override
    158    public M getMiddle() {
    159        return middle;
    160    }
    161
    162    /**
    163     * {@inheritDoc}
    164     */
    165    @Override
    166    public R getRight() {
    167        return right;
    168    }
    169}
    170