Interface for simple container classes that allow elements to be added (accumulated) to it.

Implemetations of this interface allow elements of a given type to be added to them, and later iterated over them. The actual nature of the additions, or other restrictions are implementation dependent.

This interface doesn't specify requirements regarding to thread safety, algorithmic complexity of the additions or iteration order and behaviour.

Addition methods may throw implementation specific runtime exceptions if they cannot fulfil the request. E.g. no more pre-allocated storage available, or requirements regarding the argument is violated.