io.vavr.Tuple0 Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of vavr Show documentation
Vavr is an object-functional library for Java 8+
There is a newer version: 1.0.0-alpha-4
/*  __    __  __  __    __  ___
 * \  \  /  /    \  \  /  /  __/
 *  \  \/  /  /\  \  \/  /  /
 *   \____/__/  \__\____/__/
 *
 * Copyright 2014-2017 Vavr, http://vavr.io
 *
 * 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.
 */
package io.vavr;

/*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*\
   G E N E R A T O R   C R A F T E D
\*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/

import io.vavr.collection.Iterator;
import io.vavr.collection.List;
import io.vavr.collection.Seq;
import java.io.Serializable;
import java.util.Comparator;
import java.util.Objects;
import java.util.function.Supplier;

/**
 * A tuple of no elements which can be seen as cartesian product of no components.
 *
 * @author Daniel Dietrich
 */
public final class Tuple0 implements Tuple, Comparable, Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * The singleton instance of Tuple0.
     */
    private static final Tuple0 INSTANCE = new Tuple0 ();

    /**
     * The singleton Tuple0 comparator.
     */
    private static final Comparator COMPARATOR = (Comparator & Serializable) (t1, t2) -> 0;

    // hidden constructor, internally called
    private Tuple0 () {
    }

    /**
     * Returns the singleton instance of Tuple0.
     *
     * @return The singleton instance of Tuple0.
     */
    public static Tuple0 instance() {
        return INSTANCE;
    }

    public static  Comparator comparator() {
        return COMPARATOR;
    }

    @Override
    public int arity() {
        return 0;
    }

    @Override
    public int compareTo(Tuple0 that) {
        return 0;
    }

    /**
     * Transforms this tuple to an object of type U.
     *
     * @param f Transformation which creates a new object of type U based on this tuple's contents.
     * @param  type of the transformation result
     * @return An object of type U
     * @throws NullPointerException if {@code f} is null
     */
    public  U apply(Supplier f) {
        Objects.requireNonNull(f, "f is null");
        return f.get();
    }

    @Override
    public Seq toSeq() {
        return List.empty();
    }

    // -- Object

    @Override
    public boolean equals(Object o) {
        return o == this;
    }

    @Override
    public int hashCode() {
        return 1;
    }

    @Override
    public String toString() {
        return "()";
    }

    // -- Serializable implementation

    /**
     * Instance control for object serialization.
     *
     * @return The singleton instance of Tuple0.
     * @see java.io.Serializable
     */
    private Object readResolve() {
        return INSTANCE;
    }

}