java11-vavr-either

Reference: https://www.vavr.io/vavr-docs/#_either
Reference: https://static.javadoc.io/io.vavr/vavr/0.9.2/io/vavr/control/Either.html

preface

Either represents a value of two possible types. An Either is either a Left or a Right. If the given Either is a Right and projected to a Left, the Left operations have no effect on the Right value. If the given Either is a Left and projected to a Right, the Right operations have no effect on the Left value. If a Left is projected to a Left or a Right is projected to a Right, the operations have an effect.

Note that Try<T> is isomorphic to Either<Throwable, T>.

By convention the success case is Right and the failure is Left.

project description

We provide description and tests for Either's methods.

Please refer my other github projects:

• https://github.com/mtumilowicz/java11-vavr-option
• https://github.com/mtumilowicz/java11-vavr-try because we won't provide examples to the similar methods described in the projects mentioned above.

static methods

• <L,R> Either<L,R> left(L left) - Constructs a Either.Left
• <L,R> Either<L,R> right(R right) - Constructs a Either.Right
• <L,R> Either<L,R> narrow(Either<? extends L,? extends R> either) - Narrows a widened Either<? extends L, ? extends R> to Either<L, R> by performing a type-safe cast.
• <L,R> Either<Seq<L>,Seq<R>> sequence(Iterable<? extends Either<? extends L,? extends R>> eithers) - Reduces many Eithers into a single Either by transforming an Iterable<Either<L, R>> into a Either<Seq<L>, Seq<R>>.
• <L,R> Either<L,Seq<R>> sequenceRight(Iterable<? extends Either<? extends L,? extends R>> eithers) - Reduces many Eithers into a single Either by transforming an Iterable<Either<L, R>> into a Either<L, Seq<R>>.

instance methods

• Either<X,Y> bimap(Function<? super L,? extends X> leftMapper, Function<? super R,? extends Y> rightMapper) - Maps either the left or the right side of this disjunction.
• boolean equals(Object o)
• Option<Either<L,R>> filter(Predicate<? super R> predicate)
  • if Left returns Option.of(this)
  • if Right and predicate is satisfied returns Option.of(this)
  • if Right and predicate is not satisfied returns Option.none()
• Either<L,U> flatMap(Function<? super R,? extends Either<L,? extends U>> mapper)
  • if Right flatMaps
  • if Left returns this
• U fold(Function<? super L,? extends U> leftMapper, Function<? super R,? extends U> rightMapper)
  • if Right maps right value with rightMapper
  • if Left maps left value with leftMapper
• R get()
  • if Right returns value
  • if Left throws NoSuchElementException
• L getLeft()
• R getOrElseGet(Function<? super L,? extends R> other)
  • if Right returns value
  • if Left returns other
• <X extends Throwable> R getOrElseThrow(Function<? super L,X> exceptionFunction)
  • if Right returns value
  • if Left throws exception
• int hashCode()
• boolean isEmpty() ` @Override default boolean isEmpty() { return isLeft(); }

• boolean isLeft()
• boolean isRight()
• Either.LeftProjection<L,R> left()
• Either.RightProjection<L,R> right()
• Either<L,U> map(Function<? super R,? extends U> mapper)
  • if Right maps right value with mapper
  • if Left returns this
• Either<U,R> mapLeft(Function<? super L,? extends U> leftMapper)
• Either<L,R> orElse(Either<? extends L,? extends R> other)
  • if Right returns this
  • if Left returns left mapped by other
• Either<L,R> orElse(Supplier<? extends Either<? extends L,? extends R>> supplier)
• void orElseRun(Consumer<? super L> action) - if Left runs action
• Either<L,R> peek(Consumer<? super R> action) - if Right runs action
• Either<L,R> peekLeft(Consumer<? super L> action) if Left runs action
• Either<R,L> swap() Converts a Left to a Right and vice versa by wrapping the value in a new type.