Question

I’m working on a codebase ported from Objective C to Java. There are several usages of method chaining without nullchecks

dog.collar().tag().name()

I was looking for something similar to safe-dereferencing operator ?. in Groovy instead of having nullchecks

dog.collar?.tag?.name

This led to Maybe monad to have the notion of Nothing instead of Null. But all the implementations of Nothing i came across throw exception when value is accessed which still doesn’t solve the chaining problem. I made Nothing return a mock, which behaves like NullObject pattern. But it solves the chaining problem.

Is there anything wrong with this implementation of Nothing?

public class Nothing<T> implements Maybe<T> {

    private Class<T> klass;

    public Nothing(Class<T> klass) {
        this.klass = klass;
    }

    @Override
    public T value() {
        return mock(klass, Mockito.RETURNS_DEEP_STUBS); 
    }
}

As far as I can see

1. It feels odd to use mocking library in code
2. It doesn’t stop at the first null.
3. How do i distinguish between null result because of null reference or name actually being null? How is it distinguished in Groovy code?

Answer 1

I wouldn’t really recommend just checking for the nulls. Really, I recommend not even ever returning null, but instead throwing exceptions.

In either case, you are not going to make the code any faster by doing this null object method, and I think you’ll just end up confusing someone just because you want to replicate the feature of a different programming language. I think you should just adapt to the language you’re using.