Container to ease passing around a tuple of four objects.

Quadruple.java

/*
 * Copyright (C) 2016 Daniel Gallego Vico.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.Objects;

/**
 * Container to ease passing around a tuple of four objects.
 * This object provides a sensible implementation of equals(),
 * returning true if equals() is true on each of the contained objects.
 *
 * @param <A> first object type to store in the Quadruple
 * @param <B> second object type to store in the Quadruple
 * @param <C> third object type to store in the Quadruple
 * @param <D> fourth object type to store in the Quadruple
 */
public class Quadruple<A, B, C, D> {
    public final A first;
    public final B second;
    public final C third;
    public final D fourth;

    /**
     * Constructor for a Quadruple
     *
     * @param first - the first object in the Quadruple
     * @param second - the second object in the Quadruple
     * @param third - the third object in the Quadruple
     * @param fourth - the fourth object in the Quadruple
     */
    public Quadruple(A first, B second, C third, D fourth) {
        this.first = first;
        this.second = second;
        this.third = third;
        this.fourth = fourth;
    }

    /**
     * Checks the two objects for equality by delegating to their respective
     * {@link Object#equals(Object)} methods.
     *
     * @param o the {@link Quadruple} to which this one is to be checked for equality
     * @return true if the underlying objects of the Quadruple are considered equal
     */
    @Override
    public boolean equals(Object o) {
        if(!(o instanceof Quadruple)) {
            return false;
        }
        Quadruple<?,?,?,?> q = (Quadruple<?,?,?,?>) o;
        return Objects.equals(q.first, first)
                && Objects.equals(q.second, second)
                && Objects.equals(q.third, third)
                && Objects.equals(q.fourth, fourth);
    }

    /**
     * Compute a hash code using the hash codes of the underlying objects
     *
     * @return a hashcode on the Quadruple
     */
    @Override
    public int hashCode() {
        return (first == null ? 0 : first.hashCode())
                ^ (second == null ? 0 : second.hashCode())
                ^ (third == null ? 0 : third.hashCode())
                ^ (fourth == null ? 0 : fourth.hashCode());
    }

    /**
     * Convenience method for creating an appropriately typed Quadruple.
     *
     * @param a the first object in the Quadruple
     * @param b the second object in the Quadruple
     * @param c the third object in the Quadruple
     * @param d the fourth object in the Quadruple
     * @param <A> first object type of the Quadruple
     * @param <B> second object type of the Quadruple
     * @param <C> third object type of the Quadruple
     * @param <D> fourth object type of the Quadruple
     *
     * @return a Quadruple that is templatized with the types of a, b, c and d
     */
    public static <A, B, C, D> Quadruple<A, B, C, D> create(A a, B b, C c, D d) {
        return new Quadruple<>(a, b, c, d);
    }
}

Kotlin:

data class Quadruple<A, B, C, D>(val a: A, val b: B, val c: C, val d: D)