    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.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 *
    038 * @since 3.2
    039 */
    040public abstract class Triple<L, M, R> implements Comparable<Triple<L, M, R>>, Serializable {
    041
    042    /** Serialization version */
    043    private static final long serialVersionUID = 1L;
    044
    045    /**
    046     * An empty array.
    047     * <p>
    048     * Consider using {@link #emptyArray()} to avoid generics warnings.
    049     * </p>
    050     *
    051     * @since 3.10.
    052     */
    053    public static final Triple<?, ?, ?>[] EMPTY_ARRAY = {};
    054
    055    /**
    056     * Returns the empty array singleton that can be assigned without compiler warning.
    057     *
    058     * @param <L> the left element type
    059     * @param <M> the middle element type
    060     * @param <R> the right element type
    061     * @return the empty array singleton that can be assigned without compiler warning.
    062     *
    063     * @since 3.10.
    064     */
    065    @SuppressWarnings("unchecked")
    066    public static <L, M, R> Triple<L, M, R>[] emptyArray() {
    067        return (Triple<L, M, R>[]) EMPTY_ARRAY;
    068    }
    069
    070    /**
    071     * Obtains an immutable triple of three objects inferring the generic types.
    072     *
    073     * <p>This factory allows the triple to be created using inference to
    074     * obtain the generic types.</p>
    075     *
    076     * @param <L> the left element type
    077     * @param <M> the middle element type
    078     * @param <R> the right element type
    079     * @param left  the left element, may be null
    080     * @param middle the middle element, may be null
    081     * @param right  the right element, may be null
    082     * @return a triple formed from the three parameters, not null
    083     */
    084    public static <L, M, R> Triple<L, M, R> of(final L left, final M middle, final R right) {
    085        return ImmutableTriple.of(left, middle, right);
    086    }
    087
    088    /**
    089     * Obtains an immutable triple of three non-null 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 not be null
    098     * @param middle  the middle element, may not be null
    099     * @param right  the right element, may not be null
    100     * @return a triple formed from the three parameters, not null
    101     * @throws NullPointerException if any input is null
    102     * @since 3.13.0
    103     */
    104    public static <L, M, R> Triple<L, M, R> ofNonNull(final L left, final M middle, final R right) {
    105        return ImmutableTriple.ofNonNull(left, middle, right);
    106    }
    107
    108    /**
    109     * Constructs a new instance.
    110     */
    111    public Triple() {
    112        // empty
    113    }
    114
    115    /**
    116     * Compares the triple based on the left element, followed by the middle element,
    117     * finally the right element.
    118     * The types must be {@link Comparable}.
    119     *
    120     * @param other  the other triple, not null
    121     * @return negative if this is less, zero if equal, positive if greater
    122     */
    123    @Override
    124    public int compareTo(final Triple<L, M, R> other) {
    125      return new CompareToBuilder().append(getLeft(), other.getLeft())
    126          .append(getMiddle(), other.getMiddle())
    127          .append(getRight(), other.getRight()).toComparison();
    128    }
    129
    130    /**
    131     * Compares this triple to another based on the three elements.
    132     *
    133     * @param obj  the object to compare to, null returns false
    134     * @return true if the elements of the triple are equal
    135     */
    136    @Override
    137    public boolean equals(final Object obj) {
    138        if (obj == this) {
    139            return true;
    140        }
    141        if (obj instanceof Triple<?, ?, ?>) {
    142            final Triple<?, ?, ?> other = (Triple<?, ?, ?>) obj;
    143            return Objects.equals(getLeft(), other.getLeft())
    144                && Objects.equals(getMiddle(), other.getMiddle())
    145                && Objects.equals(getRight(), other.getRight());
    146        }
    147        return false;
    148    }
    149
    150    /**
    151     * Gets the left element from this triple.
    152     *
    153     * @return the left element, may be null
    154     */
    155    public abstract L getLeft();
    156
    157    /**
    158     * Gets the middle element from this triple.
    159     *
    160     * @return the middle element, may be null
    161     */
    162    public abstract M getMiddle();
    163
    164    /**
    165     * Gets the right element from this triple.
    166     *
    167     * @return the right element, may be null
    168     */
    169    public abstract R getRight();
    170
    171    /**
    172     * Returns a suitable hash code.
    173     *
    174     * @return the hash code
    175     */
    176    @Override
    177    public int hashCode() {
    178        return Objects.hashCode(getLeft()) ^ Objects.hashCode(getMiddle()) ^ Objects.hashCode(getRight());
    179    }
    180
    181    /**
    182     * Returns a String representation of this triple using the format {@code ($left,$middle,$right)}.
    183     *
    184     * @return a string describing this object, not null
    185     */
    186    @Override
    187    public String toString() {
    188        return "(" + getLeft() + "," + getMiddle() + "," + getRight() + ")";
    189    }
    190
    191    /**
    192     * Formats the receiver using the given format.
    193     *
    194     * <p>This uses {@link java.util.Formattable} to perform the formatting. Three variables may
    195     * be used to embed the left and right elements. Use {@code %1$s} for the left
    196     * element, {@code %2$s} for the middle and {@code %3$s} for the right element.
    197     * The default format used by {@code toString()} is {@code (%1$s,%2$s,%3$s)}.</p>
    198     *
    199     * @param format  the format string, optionally containing {@code %1$s}, {@code %2$s} and {@code %3$s}, not null
    200     * @return the formatted string, not null
    201     */
    202    public String toString(final String format) {
    203        return String.format(format, getLeft(), getMiddle(), getRight());
    204    }
    205
    206}
    207