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Bill Venners: The opposite of complexity is simplicity. I have often heard you describe your philosophy when designing Java in the early days: you didn't put something in Java unless five people screamed at you and demanded it. In one interview, you told this really good story about moving to a new apartment and something about keeping things in boxes.
James Gosling: That's actually a general principle for life that works really well. When you move to a new apartment, don't unpack. Just sort of move in, and as you need things, pull them out of the boxes. After you've been in the apartment for a couple of months, take the boxes -- don't even open them -- and just leave what's in there and throw them out.
Bill Venners: The 'don't even open them' part is important because it's very hard to throw things away once you know what they are.
James Gosling: Right, because if you open them, you say, 'oh, I can't part with that.'
Bill Venners: So would you say that simplicity is a general philosophy programmers should always have when designing programs?
James Gosling: I think in any kind of design, you must drive for simplicity all the time. If you don't, complexity will nail you. Dealing with complexity is hard enough.
In programming language design, one of the standard problems is that the language grows so complex that nobody can understand it. One of the little experiments I tried was asking people about the rules for unsigned arithmetic in C. It turns out nobody understands how unsigned arithmetic in C works. There are a few obvious things that people understand, but many people don't understand it.
So one of the most important criteria for judging a design for me is the manual. Is the manual out of control, or is it reasonably concise? You can write a pretty decent Java manual in less than 100 pages. The current Java language spec is pretty thick, but that's because it's probably the most detailed language spec ever written. It goes through all of the details. I couldn't write the Java language spec.