Do one thing, do it well, do it only

A method should do one thing, and only one thing. It should do it in the best way possible.

A method likely does one thing if

• it has few input parameters
• it doesn’t include Boolean parameters
• it has exactly one output parameter
• it is small
• it descends one level of abstraction
• it only throws one type of exception
• you cannot extract meaningful other methods
• you cannot meaningfully group its statements into sections