Page 1324 - AP Computer Science A, 7th edition

21. (D) A program that uses an abstract class must have at least one subclass that is not abstract, since instances of abstract classes cannot be created. Thus, choice E is false. Choice A is false: An abstract class can contain any number of private instance variables. Choice B is wrong—for example v1 and v2 could be initialized in a default constructor (constructor with no parameters). Choice C is incorrect: The point of an abstract class is that no instances of it will be created. The class does not need to contain any abstract methods.