[kragen]

You're replying to a comment that says "interviewing java devs of all levels... a lot more (roughly half) could trace the following code correctly." That means that the other (roughly) half of the "Java devs" interviewed found Java's pass-by-value behavior to be surprising, even though there are no exceptions to it.

So although Java's behavior is simple and consistent, the parent comment seems to flatly contradict your assertion, "If you've been programming in Java for a little while, it's very easy to have an intuitive feel for how parameters will act." It's also a perfect example of how programming in Java, or in fact any language with a parameter-passing mechanism and mutable variables, does require that knowledge, so your assertion that "Java's a stronger language for not requiring that knowledge" is nonsense.

[moss]

You're right: calling it "very easy" was overstating things to the point of absurdity. I do think Java's behavior has a big advantage in being easier to understand than the theory behind it is ("less than 10%"), but I had completely glossed over the "roughly half" point the first time I read this, and it really hurts my claim that Java's approach is trivial to understand.

That said, I stand by "not requiring that knowledge". Java's behavior is understandable without having to know about value and reference semantics. That doesn't mean it doesn't require any knowledge. Specifically, I think it requires two points: (1) Variables are just names, so reassigning a variable doesn't change anything else in the system; (2) When you call a method on an object, you might change that object.

In support of this: I've also been doing a lot of interviews recently. In my (admittedly limited) experience, the people who have had trouble with Java's parameter passing behavior are more experienced developers who've done a lot of work in other languages. Their confusion isn't from Java's behavior, it's the caution about pass-by-reference that they've brought over from C and C++. I don't really see junior people making this mistake. So I suspect having just a little knowledge of the value vs. reference issue makes Java harder to understand, by bringing up new and confusing possibilities.

But, like I said, my experience is limited. If you do see new developers being confused by this aspect of Java (or Python, Ruby, or other languages with similar semantics), I'd be interested to hear about it.