Nulls in every type and checked exceptions in Java?

Question

I know that null being added to every type in Java is a source of much frustration regarding the language's type system. At the same time I generally hear complaining about checked exceptions - that they clutter interfaces, encourage exception swallowing, etc. It seems to me like null inhabiting every type is a way around the language - like I want the type of this to be X, but it's actually X or null; it just doesn't look like that and is easy to forget. Don't checked exceptions provide a way for the type of something to be X or throws Exception instead of it appearing to just be X? It provides an in-code way to specify how something can fail.

Nulls in every type and unchecked exceptions seem like they are dual concepts, but one is scorned and the other praised. Why is that?

Answer 1

Most people who scorn NULLs have never actually written in a language without them. People who scorn checked exceptions have written in a language with them. People have seen the downsides of checked exceptions much more then the downsides of NULL-less programming. Popular languages have used checked exceptions, but no popular language has gotten rid of NULLs.

Both of these idea are trying to prove some notion correctness in a program. In my view, that sounds like a good idea in theory but tends to fall apart in practice. The effort and restrictions placed on your attempts to prove correctness are generally not worth the benefits of the limited amount of correctness being proved.

Many specific criticisms of checked exceptions exist. I'm not going to repeat them all here, I'm sure that's been done to death. NULL may not have the same issues show up. However, the lack of widespread NULL-less programming may mean that we simply haven't had time to see them. Or perhaps checked exceptions simply produce more problems then NULL-less programming does.