JarCastingeither
A simple algebraic data type for java. An Either is commonly used to represent a result that might fail, where the left side contains the error result and the right side contains the success result. You can think of this as a more powerful alternative to Optional. Plays nicely with Java 8 types.
Artifacts
Gradle
compile 'com.steinf:either:1.0.4'
Maven
<dependency>
<groupId>com.steinf</groupId>
<artifactId>either</artifactId>
<version>1.0.4</version>
</dependency>
Examples
Create an either
Either<String, Integer> e = Either.right(2);
Either<String, Integer> e = Either.left("FAIL");
Either<String, Integer> e = Either.either(() -> "FAIL", () -> 2); // right biased
Either<String, Integer> e = Either.fromOptional(Optional.of(2));
Either<String, Integer> e = Either.fromOptionalOrElse(Optional.empty(), () -> "FAIL");
Extract the right or left value
Either<String, Integer> e = Either.right(20);
e.getRight() // == 20
e.getLeft() // throws NoSuchElementException
Either<String, Integer> e = Either.left(20);
e.getLeft() // == 20
e.getRight() // throws NoSuchElementException
Check whether the either isLeft or isRight
Either.right(20).isRight() // true
Either.right(20).isLeft() // false
map over an either
Either.right(20)
.map(e -> e * 10); // == Either.right(200)
Combine either with flatMap or andThen
Either.right("right")
.flatMap(rightValue -> Either.right(rightValue + " side")); // == EIther.right("right side")
fold an either into a value
Either.right("right")
.fold(f -> "left", f -> f + " side"); // == "right side"
Either.left("left")
.fold(f -> f + " side", f -> "right"); // == "left side"
accept an either
Either.right("right")
.accept(l -> {}, r -> {});
Either.right("right")
.accept(r -> {});
Extract the value orElse get the provided value if Left
Either.left(FALSE);
.orElse("right"); // == "right"
Either.right(10);
.orElse(99); // == 10
Extract the value orElseGet get the provided value if Left
Either.left(FALSE);
.orElseGet(() -> "right"); // == "right"
Either.right(10);
.orElseGet(() -> 99); // == 10
Extract the value orElseThrow if Left
Either.left(FALSE);
.orElseThrow(() -> new RuntimeException("Errr")); // throws RuntimeException
Either.right(100);
.orElseThrow(() -> new RuntimeException("Errr")); // == 100
Filter the right side values from a stream
Stream<Either<String, String>> eithers = Stream.of(
Either.left("1"),
Either.right("2"),
Either.right("3"));
eithers
.flatMap(Either.values())
.collect(toList()); // == [2, 3]
Convert toOptional
Either.left(FALSE)
.toOptional(); // == Optional.empty()
Either.right(10);
.toOptional(); // == Optional.of(10)