An abstract class is a generalization concept. It is a class you invent to only use as a base class for inheritance but not to instantiate objects from.
And abstract datatype (ADT) is not necessarily an OOP concept. It is an older term to describe the concepts of for example Stack and Queue in terms of their functionality, without describing the implementation.
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
