Either class using Lightweight Stream API

Either.java

public final class Either<Left, Right> {
  private final Optional<Left> left;
  private final Optional<Right> right;

  private Either(Optional<Left> left, Optional<Right> right) {
    this.left = left;
    this.right = right;
  }

  public static <Left, Right> Either<Left, Right> left(@NonNull Left value) {
    return new Either<>(Optional.of(value), Optional.empty());
  }

  public static <Left, Right> Either<Left, Right> right(@NonNull Right value) {
    return new Either<>(Optional.empty(), Optional.of(value));
  }

  public <T> Either<T, Right> mapLeft(Function<? super Left, ? extends T> func) {
    return new Either<>(this.left.map(func), this.right);
  }

  public <T> Either<Left, T> mapRight(Function<? super Right, ? extends T> func) {
    return new Either<>(this.left, this.right.map(func));
  }

  public void apply(Consumer<? super Left> lConsumer, Consumer<? super Right> rConsumer) {
    this.left.ifPresent(lConsumer);
    this.right.ifPresent(rConsumer);
  }
}