I'm curious as well, I understand the bug / typo, but I don't think I've seen it more than a handful in 20+ years of C-like languages (mostly game development). In contrast, typing a single '=' instead of '==' seems a more common error IME (although still not frequent enough to drive me towards Yoda conditions to catch it).
Why do you think you are encountering this particular mistake so often? Is it something about your projects, your organization, your colleagues, or Java itself?
It's a braino, I think. Instead of the right thing, which would be what mathgladiator posted below, this is a guaranteed null pointer exception when obj actually is null.
Which is semantically correct due to the fail-fast evaluate of AND, it does require a double check since it's strange from a logic point of view. This is one the reasons that brace languages are hard to optimize since you can't commute things that ought to commute.
Static code analysis has a long-term benefit as well as the more obvious short-term benefit. That is, it teaches us to be better developers as we strive to have the static analysis catch less issues in our code the next time [1]. I used static analysis to improve my style for C, Python, and most recently Ruby [2].
I think it had a lasting effect on my personal coding habits. But every once in a while, I will use the tools on my new code and it still finds things. I would probably benefit from being more persistent in using these tools.
[1]: This assumes that the issues caught be your static analysis tool are valid concerns, which in my experience, they tend to be.
[2]: Some static analysis tools that I've used with Ruby are reek, roodi, flay, and flog. Reek and roodi report code smells. Flay reports structural similarities (opportunities for refactoring). And flog estimates the complexity of your methods.
Static analysis is essential for anything that lives solely in the domain of syntax and style. Detecting bad smells (including duplication and excessive complexity) from when you got tired or interrupted is perfect for it, and is a great heuristic way to find areas that need more attention. In Python and I assume Ruby, anything that bears on function is more reliably detected with unit tests.
