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Pattern matching in Java 8+
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| import java.util.Optional; | |
| import java.util.function.Function; | |
| import java.util.function.Predicate; | |
| import static java.util.Optional.empty; | |
| import static java.util.Optional.of; | |
| public class PatternMatchingExample { | |
| public static void main(String[] args) { | |
| PatternMatching<? super String, ?> pm = | |
| PatternMatching | |
| .when("world"::equals, x -> "Hello " + x) | |
| .orWhen("monde"::equals, x -> "Salut " + x); | |
| pm.matches("monde").ifPresent(System.out::println); | |
| } | |
| @FunctionalInterface | |
| interface PatternMatching<T, R> { | |
| static <T, R> PatternMatching<T, R> when(Predicate<T> predicate, Function<T, R> action) { | |
| return value -> predicate.test(value) ? of(action.apply(value)) : empty(); | |
| } | |
| default PatternMatching<T, R> orWhen(final Predicate<T> predicate, final Function<T, R> action) { | |
| return value -> { | |
| final Optional<R> result = matches(value); | |
| if (result.isPresent()) { | |
| return result; | |
| } | |
| return (predicate.test(value)) ? | |
| of(action.apply(value)) : empty(); | |
| }; | |
| } | |
| Optional<R> matches(T value); | |
| } | |
| } |
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