AP计算机教程9-13：简单多选题

于2018年6月11日由陈欣发布

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What best describes the purpose of a class’s constructor?

Initialize the fields in the object.

Determines the amount of space needed for an object and creates the object.

Names the new object.

构造函数的主要用途是初始化field，并不是分配内存空间。

Under which of these conditions is it appropriate to overload a method (ie: the class will contain two methods with the same name)?

The methods do different things.

The methods have different parameter names.

The methods have different post-conditions.

Two methods with the same name can never be included in the same class.

The methods have different numbers of parameters.

重载指的是同名method接受不同参数。

Which of the following statements about a class that contains an abstract method is (are) true?

I. You can’t have any constructors in this class.
II. This class must be declared as abstract.
III. You can’t declare any fields in this class.

Which of the following is true about abstract classes?

Abstract classes cannot be instantiated, but they can be sub-classed.

Abstract classes can be instantiated, but they cannot be sub-classed.

Abstract classes can only contain abstract methods. They can be sub-classed.

Abstract classes can only contain abstract methods. They cannot be sub-classed.

abstract class可以被继承，无法创建object。

A car dealership needs a program to store information about the cars for sale. For each car, they want to keep track of the following information: number of doors (2 or 4), whether the car has air conditioning, and its average number of miles per gallon. Which of the following is the best design?

Use four unrelated classes: Car, Doors, AirConditioning, and MilesPerGallon.

Use a class Car with three subclasses: Doors, AirConditioning, and MilesPerGallon.

Use a class Car, with fields: numDoors, hasAir, and milesPerGallon.

Use a class Car, with subclasses of Doors, AirConditioning, and MilesPerGallon.

Use classes: Doors, AirConditioning, and MilesPerGallon, each with a subclass Car.

numDoors、hasAir与milesPerGallon等信息适用包含关系，可作为Car的field。

A program is being written by a team of programmers. One programmer is implementing a class called Employee; another programmer is writing code that will use the Employee class. Which of the following aspects of the public methods and fields of the Employee class does not need to be known by both programmers?

How the methods are implemented.

The method names.

The method return types.

Constants.

The number and types of the method parameters.

面向对象编程的精髓在于method的实现细节是个黑盒子。

A bookstore is working on an on-line ordering system. For each type of published material (books, movies, audio tapes) they need to track the id, title, author(s), date published, and price. Which of the following would be the best design?

Create one class PublishedMaterial with the requested fields plus type

Create classes Book and Movie and each class has the requested fields

Create the class PublishedMaterial and have Book and Movie inherit from it all the listed fields

Create one class BookStore with the requested fields plus type

Create classes for PublishedMaterial, Books, Movies, Title, Price, ID, Authors, DatePublished

使用PublishedMaterial作为parent class，Books和Movies作为child class，Title、Price、ID、Authors、DatePublished等作为field是最好的设计。

AP计算机教程9-13：简单多选题

陈欣

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