javaslang.Tuple0 Maven / Gradle / Ivy
/* / \____ _ _ ____ ______ / \ ____ __ _______
* / / \/ \ / \/ \ / /\__\/ // \/ \ // /\__\ JΛVΛSLΛNG
* _/ / /\ \ \/ / /\ \\__\\ \ // /\ \ /\\/ \ /__\ \ Copyright 2014-2016 Javaslang, http://javaslang.io
* /___/\_/ \_/\____/\_/ \_/\__\/__/\__\_/ \_// \__/\_____/ Licensed under the Apache License, Version 2.0
*/
package javaslang;
/*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*\
G E N E R A T O R C R A F T E D
\*-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-*/
import java.io.Serializable;
import java.util.Comparator;
import java.util.Objects;
import java.util.function.Supplier;
import javaslang.collection.List;
import javaslang.collection.Seq;
/**
* A tuple of no elements which can be seen as cartesian product of no components.
*
* @author Daniel Dietrich
* @since 1.1.0
*/
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 transform(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;
}
}