Optional vs null && Stream vs loop

Lab.java

package org.codefx.lab;

import java.util.Collection;
import java.util.List;
import java.util.Optional;
import java.util.function.Function;
import java.util.function.UnaryOperator;
import java.util.stream.Stream;

class Lab {

	// WITH OPTIONAL &

	static List<Function<String, Optional<String>>> operatorsToOptional =
			List.of(
					s -> Optional.empty(),
					s -> Optional.of(new StringBuilder(s).reverse().toString()));

	// ... & stream

	static Optional<String> streamOptional(String string) {
		return operatorsToOptional.stream()
				.flatMap(operator -> operator.apply(string).stream())
				.findFirst();
	}

	// ... & loop

	static Optional<String> loopOptional(String string) {
		for (var operator : operatorsToOptional) {
			var uri = operator.apply(string);
			if (uri.isPresent())
				return uri;
		}
		return Optional.empty();
	}

	// WITH NULL & ...

	static Collection<UnaryOperator<String>> operatorsToNull =
			List.of(
					s -> null,
					s -> new StringBuilder(s).reverse().toString());

	// ... & stream

	static String streamNull(String string) {
		return operatorsToNull.stream()
				.flatMap(operator -> Stream.ofNullable(operator.apply(string)))
				.findFirst()
				.orElse(null);
	}

	// ... & loop

	static String loopNull(String string) {
		for (var operator : operatorsToNull) {
			var uri = operator.apply(string);
			if (uri != null)
				return uri;
		}
		return null;
	}

}