The following story dates back from a couple of years ago. A colleague of mine was experiencing a problem with a system we were working on. Most of the time, things were right, but from time to time, the system gave the wrong answer to a query. A quick investigation revealed that the method to calculate the result was right, but sometimes the wrong result seemed to come out anyway. The strange thing was that when the system replied with the wrong answer, it was in fact the correct answer for another query sent to the system. My colleague really didn't understand what was going on, so she called me to investigate the problem.
The little detail that the system returned the correct answer to another query, was in fact a important clue to solve the mystery. After browsing through the code for a few minutes, I found out that one of the attributes in a class was marked static. As a result, the system returned the result for the last query that entered the system, even if you asked for the result of a previous query. And that was the kind of bug I was expecting from the beginning: to me, the problem had the smell of static confusion all over it, even though I couldn't say exactly why.
My colleague was impressed, and literally asked me how I could know such a thing. The only answer I could come up with was that many years of creating many bugs had given me much experience in finding out why something was wrong. I guess that's the essence of being a senior developer too...
