Seconding my sibling richchan that it doesn't necessarily need to be "good" code, I'd suggest starting by reading the libraries — or even just the specific clas

Seconding my sibling richchan that it doesn't necessarily need to be "good" code, I'd suggest starting by reading the libraries — or even just the specific classes or functions — you like to use. You already know what they're supposed to do, so they'll be a lot easier to figure out at first— and once you do, it will provide the immediate benefit of understanding your tools. As for how you tell, a good rule of thumb is, the harder of a time you have telling how it works, the worse the code is. This is of course only a rule of thumb, but it applies doubly in the case of code where you understand well what it's supposed to be doing.