Clean Code: A Handbook of Agile Software Craftsmanship (Robert C. Martin Series)

by Robert C. Martin

We want our code to be a quick skim, not an intense study.

The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that.

FUNCTIONS SHOULD DO ONE THING. THEY SHOULD DO IT WELL. THEY SHOULD DO IT ONLY.

Side effects are lies. Your function promises to do one thing, but it also does other hidden things.

Functions should either do something or answer something, but not both.

This I contend with slightly. It may be useful to return a boolean that tells you whether or not a method has completed successfully. Many APIs (including Java) do this a lot which has sort of normalized this kind of behavior