    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. The class is also {@code final}, so a subclass
    027 * can not add undesirable behavior.</p>
    028 *
    029 * <p>#ThreadSafe# if all three objects are thread-safe</p>
    030 *
    031 * @param <L> the left element type
    032 * @param <M> the middle element type
    033 * @param <R> the right element type
    034 *
    035 * @since 3.2
    036 */
    037public class ImmutableTriple<L, M, R> extends Triple<L, M, R> {
    038
    039    /**
    040     * An empty array.
    041     * <p>
    042     * Consider using {@link #emptyArray()} to avoid generics warnings.
    043     * </p>
    044     *
    045     * @since 3.10.
    046     */
    047    public static final ImmutableTriple<?, ?, ?>[] EMPTY_ARRAY = {};
    048
    049    /**
    050     * An immutable triple of nulls.
    051     */
    052    // This is not defined with generics to avoid warnings in call sites.
    053    @SuppressWarnings("rawtypes")
    054    private static final ImmutableTriple NULL = new ImmutableTriple<>(null, null, null);
    055
    056    /** Serialization version */
    057    private static final long serialVersionUID = 1L;
    058
    059    /**
    060     * Returns the empty array singleton that can be assigned without compiler warning.
    061     *
    062     * @param <L> the left element type
    063     * @param <M> the middle element type
    064     * @param <R> the right element type
    065     * @return the empty array singleton that can be assigned without compiler warning.
    066     *
    067     * @since 3.10.
    068     */
    069    @SuppressWarnings("unchecked")
    070    public static <L, M, R> ImmutableTriple<L, M, R>[] emptyArray() {
    071        return (ImmutableTriple<L, M, R>[]) EMPTY_ARRAY;
    072    }
    073
    074    /**
    075     * Returns an immutable triple of nulls.
    076     *
    077     * @param <L> the left element of this triple. Value is {@code null}.
    078     * @param <M> the middle element of this triple. Value is {@code null}.
    079     * @param <R> the right element of this triple. Value is {@code null}.
    080     * @return an immutable triple of nulls.
    081     * @since 3.6
    082     */
    083    @SuppressWarnings("unchecked")
    084    public static <L, M, R> ImmutableTriple<L, M, R> nullTriple() {
    085        return NULL;
    086    }
    087
    088    /**
    089     * Obtains an immutable triple of three objects inferring the generic types.
    090     *
    091     * <p>This factory allows the triple to be created using inference to
    092     * obtain the generic types.</p>
    093     *
    094     * @param <L> the left element type
    095     * @param <M> the middle element type
    096     * @param <R> the right element type
    097     * @param left  the left element, may be null
    098     * @param middle  the middle element, may be null
    099     * @param right  the right element, may be null
    100     * @return a triple formed from the three parameters, not null
    101     */
    102    public static <L, M, R> ImmutableTriple<L, M, R> of(final L left, final M middle, final R right) {
    103        return left != null | middle != null || right != null ? new ImmutableTriple<>(left, middle, right) : nullTriple();
    104    }
    105
    106    /**
    107     * Obtains an immutable triple of three non-null objects inferring the generic types.
    108     *
    109     * <p>This factory allows the triple to be created using inference to
    110     * obtain the generic types.</p>
    111     *
    112     * @param <L> the left element type
    113     * @param <M> the middle element type
    114     * @param <R> the right element type
    115     * @param left  the left element, may not be null
    116     * @param middle  the middle element, may not be null
    117     * @param right  the right element, may not be null
    118     * @return a triple formed from the three parameters, not null
    119     * @throws NullPointerException if any input is null
    120     * @since 3.13.0
    121     */
    122    public static <L, M, R> ImmutableTriple<L, M, R> ofNonNull(final L left, final M middle, final R right) {
    123        return of(Objects.requireNonNull(left, "left"), Objects.requireNonNull(middle, "middle"), Objects.requireNonNull(right, "right"));
    124    }
    125
    126    /** Left object */
    127    public final L left;
    128    /** Middle object */
    129    public final M middle;
    130
    131    /** Right object */
    132    public final R right;
    133
    134    /**
    135     * Create a new triple instance.
    136     *
    137     * @param left  the left value, may be null
    138     * @param middle the middle value, may be null
    139     * @param right  the right value, may be null
    140     */
    141    public ImmutableTriple(final L left, final M middle, final R right) {
    142        this.left = left;
    143        this.middle = middle;
    144        this.right = right;
    145    }
    146
    147    /**
    148     * {@inheritDoc}
    149     */
    150    @Override
    151    public L getLeft() {
    152        return left;
    153    }
    154
    155    /**
    156     * {@inheritDoc}
    157     */
    158    @Override
    159    public M getMiddle() {
    160        return middle;
    161    }
    162
    163    /**
    164     * {@inheritDoc}
    165     */
    166    @Override
    167    public R getRight() {
    168        return right;
    169    }
    170}
    171