Actually, I don't know Java that deeply, mostly from how it interacts with kotlin=)

After discovering super looks much better than initCause 👍

Also, if you decide to start from scratch, feel free to ask me for some suggestions and help with the API.

I'd do it in Kotlin, as it requires much less boilerplate - like you can use default parameters and no need to duplicate methods for different parameter variants.

But even if you decide to stick with Java for your own reasons, there're some stuff I can help with.

e.g. in Java world builder pattern is often used, so you can build things like options inline, like

new Client(
    endpoint, 
    Options.Builder()
		.setToken("")
		.build(), 
    listener
);

An other thing I'd change is updating ResultCallback to be safer - right now you can pass both exception and success result, which is ambiguous

Thanks, I will keep this in mind 👍 It was my first and the only Java project, so some not idiomatic and naive things may be here and there. Luckily some things may be gradually improved. I suppose builder may be introduced in backwards compatible way. Harder with ResultCallback I think... Our Swift SDK utilizes Result type.

That's what I was able to find for Java:

public class Result<T> {
    private T result;
    private Throwable error;

    private Result(T result, Throwable error) {
        this.result = result;
        this.error = error;
    }

    public static <T> Result<T> success(T result) {
        return new Result<>(result, null);
    }

    public static <T> Result<T> error(Throwable error) {
        return new Result<>(null, error);
    }

    public T getResult() {
        return result;
    }

    public Throwable getError() {
        return error;
    }

    public boolean isSuccess() {
        return error == null;
    }

    public boolean isError() {
        return error != null;
    }
}

You mean sth like this right?

Coming back to pr, so let's proceed with this PR then instead of #54.

Yeah, you can even use kotlin.Result - it should work in Java, not sure how good is its API from Java side, but for kotlin lib users it'll be nice =)

I guess it's a good thing, but adding types from Kotlin goes beyond my current understanding :) I'd prefer keeping things simple here, to avoid problems with maintaining. I just opened a separate issue for keeping Result type in mind.