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