src/main/java/javascalautils/RightProjection.java
public Option<Either<L, R>> filter(Predicate<R> predicate) {
        return Option.apply(exists(predicate) ? either : null);
    }
public Option<Either<L, R>> filter(Predicate<R> predicate) {
        return Option.apply(exists(predicate) ? either : null);
    }
Returns a {@link Some} wrapping the {@link Either} if it's a {@link Right} and the value of the {@link Right} matches the predicate, else {@link None} .

@param predicate
The predicate to apply
@return The resulting Option of the filter operation
@since 1.1