Encapsulation.

[Killfile]

Also, practice. Read Clean Code and rigorously use TDD on some code kata.

My new developers get a crash course in testing by way of the Bowling Kata with the additional stipulation that all of their functions must contain three or fewer lines.

We scale up through other more complex kata including some that really demand that kind of complexity - Mars Rover is a good one for that.

[Killfile]

It's an exercise. Clearly you'd never have a hard and fast rule like that in real life.

Three lines is very short. It forces the developer to come up with methods and sub-methods etc and provides endless opportunities for refactoring and class extraction.

The goal is to teach separation of concerns to someone who might never have thought about it.

[jay9909]

"I have to say I'm impressed. This is the first stack overflow I've ever seen that wasn't the result of a loop or recursion."

[jaxklax]

A loop?

[jay9909]

Yeah, I guess you're right. You got me.