Tuple1.java

/*                        __    __  __  __    __  ___
 *                       \  \  /  /    \  \  /  /  __/
 *                        \  \/  /  /\  \  \/  /  /
 *                         \____/__/  \__\____/__/.ɪᴏ
 * ᶜᵒᵖʸʳᶦᵍʰᵗ ᵇʸ ᵛᵃᵛʳ ⁻ ˡᶦᶜᵉⁿˢᵉᵈ ᵘⁿᵈᵉʳ ᵗʰᵉ ᵃᵖᵃᶜʰᵉ ˡᶦᶜᵉⁿˢᵉ ᵛᵉʳˢᶦᵒⁿ ᵗʷᵒ ᵈᵒᵗ ᶻᵉʳᵒ
 */
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.Function;

/**
 * A tuple of one element which can be seen as cartesian product of one component.
 *
 * @param <T1> type of the 1st element
 * @author Daniel Dietrich
 */
public final class Tuple1<T1> implements Tuple, Comparable<Tuple1<T1>>, Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * The 1st element of this tuple.
     */
    public final T1 _1;

    /**
     * Constructs a tuple of one element.
     *
     * @param t1 the 1st element
     */
    public Tuple1(T1 t1) {
        this._1 = t1;
    }

    public static <T1> Comparator<Tuple1<T1>> comparator(Comparator<? super T1> t1Comp) {
        return (Comparator<Tuple1<T1>> & Serializable) (t1, t2) -> {
            final int check1 = t1Comp.compare(t1._1, t2._1);
            if (check1 != 0) {
                return check1;
            }

            // all components are equal
            return 0;
        };
    }

    @SuppressWarnings("unchecked")
    private static <U1 extends Comparable<? super U1>> int compareTo(Tuple1<?> o1, Tuple1<?> o2) {
        final Tuple1<U1> t1 = (Tuple1<U1>) o1;
        final Tuple1<U1> t2 = (Tuple1<U1>) o2;

        final int check1 = t1._1.compareTo(t2._1);
        if (check1 != 0) {
            return check1;
        }

        // all components are equal
        return 0;
    }

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

    @Override
    public int compareTo(Tuple1<T1> that) {
        return Tuple1.compareTo(this, that);
    }

    /**
     * Getter of the 1st element of this tuple.
     *
     * @return the 1st element of this Tuple.
     */
    public T1 _1() {
        return _1;
    }

    /**
     * Sets the 1st element of this tuple to the given {@code value}.
     *
     * @param value the new value
     * @return a copy of this tuple with a new value for the 1st element of this Tuple.
     */
    public Tuple1<T1> update1(T1 value) {
        return new Tuple1<>(value);
    }

    /**
     * Maps the components of this tuple using a mapper function.
     *
     * @param mapper the mapper function
     * @param <U1> new type of the 1st component
     * @return A new Tuple of same arity.
     * @throws NullPointerException if {@code mapper} is null
     */
    public <U1> Tuple1<U1> map(Function<? super T1, ? extends U1> mapper) {
        Objects.requireNonNull(mapper, "mapper is null");
        return Tuple.of(mapper.apply(_1));
    }

    /**
     * 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 <U> type of the transformation result
     * @return An object of type U
     * @throws NullPointerException if {@code f} is null
     */
    public <U> U apply(Function<? super T1, ? extends U> f) {
        Objects.requireNonNull(f, "f is null");
        return f.apply(_1);
    }

    @Override
    public Seq<?> toSeq() {
        return List.of(_1);
    }

    // -- Object

    @Override
    public boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof Tuple1)) {
            return false;
        } else {
            final Tuple1<?> that = (Tuple1<?>) o;
            return Objects.equals(this._1, that._1);
        }
    }

    // if _1 == null, hashCode() returns Objects.hash(new T1[] { null }) = 31 instead of 0 = Objects.hash(null)
    @Override
    public int hashCode() {
        return Objects.hash(_1);
    }

    @Override
    public String toString() {
        return "(" + _1 + ")";
    }

}