Comment by ajuc

A common problem with code written like that is checking the same preconditions repeatedly (or worse - never) and transforming data one way and back for no reason. I remember a bug I helped fix a fresh graduate that joined our project. It crashed with NPE when a list was empty. It's weird cause empty list should cause IndexOutOfBound if anything and the poor guy was stumped.

I looked at call stack and we got list as input then it was changed to null if it was empty then it was checked for size and in yet another function it was dereferenced and indexed.

Guy was trying to fix it by adding yet another if then else 5 levels in callstack below the first time it was checked for size. No doubt then another intern would have added even more checks ;)

If you don't know what happens to your data in your program you're doing voodoo programming.