The noun abstract means a content summary of a book, article, or formal speech. The adjective abstract means existing in thought or as an idea, but not having a physical or concrete existence. The verb to abstract means to consider (something) theoretically or separately from something else.
That is why an interface is called an abstraction—because it captures only method signatures and does not describe how the result is achieved. Various implementations of the same interface—different classes—may behave quite differently, even if they receive the same parameters and return the same results. The last statement is a loaded one because we have not defined the term behavior. Let's do it now.
The behavior of a class or its objects is defined by the actions its methods perform and the results they return. If a method...