    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.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 * @since 3.2
    034 */
    035public class ImmutableTriple<L, M, R> extends Triple<L, M, R> {
    036
    037    /**
    038     * An empty array.
    039     * <p>
    040     * Consider using {@link #emptyArray()} to avoid generics warnings.
    041     * </p>
    042     *
    043     * @since 3.10
    044     */
    045    public static final ImmutableTriple<?, ?, ?>[] EMPTY_ARRAY = {};
    046
    047    /**
    048     * An immutable triple of nulls.
    049     */
    050    // This is not defined with generics to avoid warnings in call sites.
    051    @SuppressWarnings("rawtypes")
    052    private static final ImmutableTriple NULL = new ImmutableTriple<>(null, null, null);
    053
    054    /** Serialization version. */
    055    private static final long serialVersionUID = 1L;
    056
    057    /**
    058     * Gets the empty array singleton that can be assigned without compiler warning.
    059     *
    060     * @param <L> the left element type.
    061     * @param <M> the middle element type.
    062     * @param <R> the right element type.
    063     * @return the empty array singleton that can be assigned without compiler warning.
    064     * @since 3.10
    065     */
    066    @SuppressWarnings("unchecked")
    067    public static <L, M, R> ImmutableTriple<L, M, R>[] emptyArray() {
    068        return (ImmutableTriple<L, M, R>[]) EMPTY_ARRAY;
    069    }
    070
    071    /**
    072     * Gets the immutable triple of nulls singleton.
    073     *
    074     * @param <L> the left element of this triple. Value is {@code null}.
    075     * @param <M> the middle element of this triple. Value is {@code null}.
    076     * @param <R> the right element of this triple. Value is {@code null}.
    077     * @return an immutable triple of nulls.
    078     * @since 3.6
    079     */
    080    @SuppressWarnings("unchecked")
    081    public static <L, M, R> ImmutableTriple<L, M, R> nullTriple() {
    082        return NULL;
    083    }
    084
    085    /**
    086     * Creates an immutable triple of three objects inferring the generic types.
    087     *
    088     * @param <L> the left element type.
    089     * @param <M> the middle element type.
    090     * @param <R> the right element type.
    091     * @param left  the left element, may be null.
    092     * @param middle  the middle element, may be null.
    093     * @param right  the right element, may be null.
    094     * @return an immutable triple formed from the three parameters, not null.
    095     */
    096    public static <L, M, R> ImmutableTriple<L, M, R> of(final L left, final M middle, final R right) {
    097        return left != null | middle != null || right != null ? new ImmutableTriple<>(left, middle, right) : nullTriple();
    098    }
    099
    100    /**
    101     * Creates an immutable triple of three non-null objects inferring the generic types.
    102     *
    103     * @param <L> the left element type.
    104     * @param <M> the middle element type.
    105     * @param <R> the right element type.
    106     * @param left  the left element, may not be null.
    107     * @param middle  the middle element, may not be null.
    108     * @param right  the right element, may not be null.
    109     * @return an immutable triple formed from the three parameters, not null.
    110     * @throws NullPointerException if any input is null.
    111     * @since 3.13.0
    112     */
    113    public static <L, M, R> ImmutableTriple<L, M, R> ofNonNull(final L left, final M middle, final R right) {
    114        return of(Objects.requireNonNull(left, "left"), Objects.requireNonNull(middle, "middle"), Objects.requireNonNull(right, "right"));
    115    }
    116
    117    /** Left object. */
    118
    119    public final L left;
    120    /** Middle object. */
    121    public final M middle;
    122
    123    /** Right object. */
    124    public final R right;
    125
    126    /**
    127     * Constructs a new triple instance.
    128     *
    129     * @param left  the left value, may be null.
    130     * @param middle the middle value, may be null.
    131     * @param right  the right value, may be null.
    132     */
    133    public ImmutableTriple(final L left, final M middle, final R right) {
    134        this.left = left;
    135        this.middle = middle;
    136        this.right = right;
    137    }
    138
    139    /**
    140     * {@inheritDoc}
    141     */
    142    @Override
    143    public L getLeft() {
    144        return left;
    145    }
    146
    147    /**
    148     * {@inheritDoc}
    149     */
    150    @Override
    151    public M getMiddle() {
    152        return middle;
    153    }
    154
    155    /**
    156     * {@inheritDoc}
    157     */
    158    @Override
    159    public R getRight() {
    160        return right;
    161    }
    162}
    163