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