Writing your first generic

A type parameter is a relationship

A generic is worth adding when two positions in a signature must agree — the element of the array you pass in and the element you get back. If a type parameter appears only once in a signature, it is not relating anything and a plain type would say the same thing more clearly.

Good generic APIs are inferred, not annotated. If callers have to spell out the parameter every time, the signature has failed at the one job it had.

Name parameters for what they mean. A tree of T, U, and V is legal and unreadable.