In this talk (recorded at Javapolis), Joshua Block presents guidelines about how to design good APIs. I highlighted what i think are the most important parts of the talk:

  • Functionality should be easy to explain: If it’s hard to name, that’s generally a bad sign
  • Good names drive development
  • Be amenable to splitting and merging modules (If names are nasty, take a step back and make things easy to describe)
  • When in doubt, leave it out
  • You can always add, but tou cannot take it out
  • Implementation Should Not Impact API
  • Always omit implementation details
  • Inhibit freedom to change implementation
  • Don’t let implementation details “leak” into API (For example: Serializable, hash functions)
  • Minimize Accessibility of Everything (This maximizes information hiding)
  • Public classes should’nt have public fields
  • API should be easy to learn, read and use: It should be consistent, it’s a little language
  • Documentation matters (Example: Method contract between it and it’s clients)
  • Think of preconditions, postconditions, side-effects
  • Don’t Transliterate API’s
    • What’s the problem it solves?
    • What shoud abstractions did it use?
  • Don’t Make the Client Do Anything The Module Could do
  • Throw Exceptions to Indicate Exceptional Conditions

When you see the talk, post your comments here.