    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.io.Serializable;
    020import java.util.Objects;
    021
    022import org.apache.commons.lang3.builder.CompareToBuilder;
    023
    024/**
    025 * A triple consisting of three elements.
    026 *
    027 * <p>This class is an abstract implementation defining the basic API.
    028 * It refers to the elements as 'left', 'middle' and 'right'.</p>
    029 *
    030 * <p>Subclass implementations may be mutable or immutable.
    031 * However, there is no restriction on the type of the stored objects that may be stored.
    032 * If mutable objects are stored in the triple, then the triple itself effectively becomes mutable.</p>
    033 *
    034 * @param <L> the left element type.
    035 * @param <M> the middle element type.
    036 * @param <R> the right element type.
    037 * @since 3.2
    038 */
    039public abstract class Triple<L, M, R> implements Comparable<Triple<L, M, R>>, Serializable {
    040
    041    /** Serialization version */
    042    private static final long serialVersionUID = 1L;
    043
    044    /**
    045     * An empty array.
    046     * <p>
    047     * Consider using {@link #emptyArray()} to avoid generics warnings.
    048     * </p>
    049     *
    050     * @since 3.10
    051     */
    052    public static final Triple<?, ?, ?>[] EMPTY_ARRAY = {};
    053
    054    /**
    055     * Returns the empty array singleton that can be assigned without compiler warning.
    056     *
    057     * @param <L> the left element type.
    058     * @param <M> the middle element type.
    059     * @param <R> the right element type.
    060     * @return the empty array singleton that can be assigned without compiler warning.
    061     * @since 3.10
    062     */
    063    @SuppressWarnings("unchecked")
    064    public static <L, M, R> Triple<L, M, R>[] emptyArray() {
    065        return (Triple<L, M, R>[]) EMPTY_ARRAY;
    066    }
    067
    068    /**
    069     * Obtains an immutable triple of three objects inferring the generic types.
    070     *
    071     * @param <L> the left element type.
    072     * @param <M> the middle element type.
    073     * @param <R> the right element type.
    074     * @param left  the left element, may be null.
    075     * @param middle the middle element, may be null.
    076     * @param right  the right element, may be null.
    077     * @return an immutable triple formed from the three parameters, not null.
    078     */
    079    public static <L, M, R> Triple<L, M, R> of(final L left, final M middle, final R right) {
    080        return ImmutableTriple.of(left, middle, right);
    081    }
    082
    083    /**
    084     * Obtains an immutable triple of three non-null objects inferring the generic types.
    085     *
    086     * @param <L> the left element type.
    087     * @param <M> the middle element type.
    088     * @param <R> the right element type.
    089     * @param left  the left element, may not be null.
    090     * @param middle  the middle element, may not be null.
    091     * @param right  the right element, may not be null.
    092     * @return an immutable triple formed from the three parameters, not null.
    093     * @throws NullPointerException if any input is null.
    094     * @since 3.13.0
    095     */
    096    public static <L, M, R> Triple<L, M, R> ofNonNull(final L left, final M middle, final R right) {
    097        return ImmutableTriple.ofNonNull(left, middle, right);
    098    }
    099
    100    /**
    101     * Constructs a new instance.
    102     */
    103    public Triple() {
    104        // empty
    105    }
    106
    107    /**
    108     * Compares the triple based on the left element, followed by the middle element,
    109     * finally the right element.
    110     * The types must be {@link Comparable}.
    111     *
    112     * @param other  the other triple, not null.
    113     * @return negative if this is less, zero if equal, positive if greater.
    114     */
    115    @Override
    116    public int compareTo(final Triple<L, M, R> other) {
    117      return new CompareToBuilder().append(getLeft(), other.getLeft())
    118          .append(getMiddle(), other.getMiddle())
    119          .append(getRight(), other.getRight()).toComparison();
    120    }
    121
    122    /**
    123     * Compares this triple to another based on the three elements.
    124     *
    125     * @param obj  the object to compare to, null returns false.
    126     * @return true if the elements of the triple are equal.
    127     */
    128    @Override
    129    public boolean equals(final Object obj) {
    130        if (obj == this) {
    131            return true;
    132        }
    133        if (obj instanceof Triple<?, ?, ?>) {
    134            final Triple<?, ?, ?> other = (Triple<?, ?, ?>) obj;
    135            return Objects.equals(getLeft(), other.getLeft())
    136                && Objects.equals(getMiddle(), other.getMiddle())
    137                && Objects.equals(getRight(), other.getRight());
    138        }
    139        return false;
    140    }
    141
    142    /**
    143     * Gets the left element from this triple.
    144     *
    145     * @return the left element, may be null.
    146     */
    147    public abstract L getLeft();
    148
    149    /**
    150     * Gets the middle element from this triple.
    151     *
    152     * @return the middle element, may be null.
    153     */
    154    public abstract M getMiddle();
    155
    156    /**
    157     * Gets the right element from this triple.
    158     *
    159     * @return the right element, may be null.
    160     */
    161    public abstract R getRight();
    162
    163    /**
    164     * Returns a suitable hash code.
    165     * <p>
    166     * The hash code is adapted from the definition in {@code Map.Entry}.
    167     * </p>
    168     *
    169     * @return the hash code.
    170     */
    171    @Override
    172    public int hashCode() {
    173        // See Map.Entry API specification
    174        return Objects.hashCode(getLeft()) ^ Objects.hashCode(getMiddle()) ^ Objects.hashCode(getRight());
    175    }
    176
    177    /**
    178     * Returns a String representation of this triple using the format {@code (left,middle,right)}.
    179     *
    180     * @return a string describing this object, not null.
    181     */
    182    @Override
    183    public String toString() {
    184        return "(" + getLeft() + "," + getMiddle() + "," + getRight() + ")";
    185    }
    186
    187    /**
    188     * Formats the receiver using the given format.
    189     *
    190     * <p>This uses {@link java.util.Formattable} to perform the formatting. Three variables may
    191     * be used to embed the left and right elements. Use {@code %1$s} for the left
    192     * element, {@code %2$s} for the middle and {@code %3$s} for the right element.
    193     * The default format used by {@code toString()} is {@code (%1$s,%2$s,%3$s)}.</p>
    194     *
    195     * @param format  the format string, optionally containing {@code %1$s}, {@code %2$s} and {@code %3$s}, not null.
    196     * @return the formatted string, not null.
    197     */
    198    public String toString(final String format) {
    199        return String.format(format, getLeft(), getMiddle(), getRight());
    200    }
    201
    202}
    203