    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
    019/**
    020 * <p>An immutable triple consisting of three {@code Object} elements.</p>
    021 *
    022 * <p>Although the implementation is immutable, there is no restriction on the objects
    023 * that may be stored. If mutable objects are stored in the triple, then the triple
    024 * itself effectively becomes mutable. The class is also {@code final}, so a subclass
    025 * can not add undesirable behaviour.</p>
    026 *
    027 * <p>#ThreadSafe# if all three objects are thread-safe</p>
    028 *
    029 * @param <L> the left element type
    030 * @param <M> the middle element type
    031 * @param <R> the right element type
    032 *
    033 * @since 3.2
    034 */
    035public final class ImmutableTriple<L, M, R> extends Triple<L, M, R> {
    036
    037    /**
    038     * An immutable triple of nulls.
    039     */
    040    // This is not defined with generics to avoid warnings in call sites.
    041    @SuppressWarnings("rawtypes")
    042    private static final ImmutableTriple NULL = of(null, null, null);
    043
    044    /** Serialization version */
    045    private static final long serialVersionUID = 1L;
    046
    047    /**
    048     * Returns an immutable triple of nulls.
    049     *
    050     * @param <L> the left element of this triple. Value is {@code null}.
    051     * @param <M> the middle element of this triple. Value is {@code null}.
    052     * @param <R> the right element of this triple. Value is {@code null}.
    053     * @return an immutable triple of nulls.
    054     * @since 3.6
    055     */
    056    @SuppressWarnings("unchecked")
    057    public static <L, M, R> ImmutableTriple<L, M, R> nullTriple() {
    058        return NULL;
    059    }
    060
    061    /** Left object */
    062    public final L left;
    063    /** Middle object */
    064    public final M middle;
    065    /** Right object */
    066    public final R right;
    067
    068    /**
    069     * <p>Obtains an immutable triple of three objects inferring the generic types.</p>
    070     *
    071     * <p>This factory allows the triple to be created using inference to
    072     * obtain the generic types.</p>
    073     *
    074     * @param <L> the left element type
    075     * @param <M> the middle element type
    076     * @param <R> the right element type
    077     * @param left  the left element, may be null
    078     * @param middle  the middle element, may be null
    079     * @param right  the right element, may be null
    080     * @return a triple formed from the three parameters, not null
    081     */
    082    public static <L, M, R> ImmutableTriple<L, M, R> of(final L left, final M middle, final R right) {
    083        return new ImmutableTriple<>(left, middle, right);
    084    }
    085
    086    /**
    087     * Create a new triple instance.
    088     *
    089     * @param left  the left value, may be null
    090     * @param middle the middle value, may be null
    091     * @param right  the right value, may be null
    092     */
    093    public ImmutableTriple(final L left, final M middle, final R right) {
    094        super();
    095        this.left = left;
    096        this.middle = middle;
    097        this.right = right;
    098    }
    099
    100    //-----------------------------------------------------------------------
    101    /**
    102     * {@inheritDoc}
    103     */
    104    @Override
    105    public L getLeft() {
    106        return left;
    107    }
    108
    109    /**
    110     * {@inheritDoc}
    111     */
    112    @Override
    113    public M getMiddle() {
    114        return middle;
    115    }
    116
    117    /**
    118     * {@inheritDoc}
    119     */
    120    @Override
    121    public R getRight() {
    122        return right;
    123    }
    124}
    125