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     * <p>This factory allows the triple to be created using inference to
089     * obtain the generic types.</p>
090     *
091     * @param <L> the left element type.
092     * @param <M> the middle element type.
093     * @param <R> the right element type.
094     * @param left  the left element, may be null.
095     * @param middle  the middle element, may be null.
096     * @param right  the right element, may be null.
097     * @return a triple formed from the three parameters, not null.
098     */
099    public static <L, M, R> ImmutableTriple<L, M, R> of(final L left, final M middle, final R right) {
100        return left != null | middle != null || right != null ? new ImmutableTriple<>(left, middle, right) : nullTriple();
101    }
102
103    /**
104     * Creates an immutable triple of three non-null objects inferring the generic types.
105     *
106     * <p>This factory allows the triple to be created using inference to
107     * obtain the generic types.</p>
108     *
109     * @param <L> the left element type.
110     * @param <M> the middle element type.
111     * @param <R> the right element type.
112     * @param left  the left element, may not be null.
113     * @param middle  the middle element, may not be null.
114     * @param right  the right element, may not be null.
115     * @return a triple formed from the three parameters, not null.
116     * @throws NullPointerException if any input is null.
117     * @since 3.13.0
118     */
119    public static <L, M, R> ImmutableTriple<L, M, R> ofNonNull(final L left, final M middle, final R right) {
120        return of(Objects.requireNonNull(left, "left"), Objects.requireNonNull(middle, "middle"), Objects.requireNonNull(right, "right"));
121    }
122
123    /** Left object. */
124
125    public final L left;
126    /** Middle object. */
127    public final M middle;
128
129    /** Right object. */
130    public final R right;
131
132    /**
133     * Constructs a new triple instance.
134     *
135     * @param left  the left value, may be null.
136     * @param middle the middle value, may be null.
137     * @param right  the right value, may be null.
138     */
139    public ImmutableTriple(final L left, final M middle, final R right) {
140        this.left = left;
141        this.middle = middle;
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 M getMiddle() {
158        return middle;
159    }
160
161    /**
162     * {@inheritDoc}
163     */
164    @Override
165    public R getRight() {
166        return right;
167    }
168}
169