either

Story

Plenty of Either classes out there, but I found most of them too tedious. I needed a pragmatic Either that would keep the client code somewhat clean.

Totally inspired by the Either classes found in vavr.io, atlassians fugue and Playframeworks F.Either.

Usage

To get started you add either as a dependency to Maven:

<dependency>
  <groupId>io.github.franzgranlund</groupId>
  <artifactId>either</artifactId>
  <version>1.3</version>
</dependency>

package io.github.franzgranlund;

public class App
{
    private static Either<String, Integer> compute(Integer i) {
        return i > 5 ? Either.left("I'm sorry Dave, I'm afraid I can't do that") : Either.right(i);
    }

    static class Cat {
        final String value = "cat";
    }
    static class Bike {
        final String value = "bike";
    }

    public static void main( String[] args )
    {
        // Prints 'anEither is a bike'
        Either<Cat, Bike> anEither = Either.right(new Bike());
        if (anEither.isRight()) {
            System.out.println("anEither is a " + anEither.getRight().value);
        }

        // Prints 'Computing successful' and sets foldResult to true
        Boolean foldResult = compute(4).fold(lhv -> {
            System.out.println(lhv);
            return false;
        }, rhv -> {
            System.out.println("Computing successful");
            return true;
        });

        // Prints 'biMapResult is a cat'
        Either<Cat, Bike> biMapResult = compute(6).bimap(lhv -> new Cat(), rhv -> new Bike());
        if (biMapResult.isLeft()) {
            System.out.println("biMapResult is a " + biMapResult.getLeft().value);
        }

        // Creates an Left 'Bike' Either since the cond-predicate is false
        // Prints 'condResult is a bike'
        Either<Bike, Cat> condResult = Either.cond(false, new Cat(), new Bike());
        if (condResult.isLeft()) {
            System.out.println("condResult is a " + condResult.getLeft().value);
        }

        // Prints 'I'm sorry Dave, I'm afraid I can't do that'
        compute(6).consume(System.out::println, rhv -> System.out.println("Batman"));
    }
}