Serializable Optional<T> using sealed interface

This library is a reimplementation of an Optional<T> that is Serializable. It aims to behave exactly like the JDK's Optional<T>, with the added benefit of being Serializable, and implemented using a sealed interface.

With this implementation you can switch over the Optional<T>:

final var message = switch (optional) {
    case Empty -> "No message";
    case Present(var message) -> message;
};

Or use an early deconstruction (JDK 21+):

if (!(optional instanceof Present(var message))) {
    return;
}
System.out.println(message);

This implementation validates all argument functions before they are used. This differs from the JDK's Optional<T> for flatMap, map, filter, and or, where they will throw an exception if the function is null.

Manual construction of Empty and Present is not recommended.

Performance benchmarks

These are currently being analysed. Preliminary results show that in some worst-case scenarios you can expect a 70% increase in nanoseconds, although this will be negligible in most applications.