Deck 10: Object-Oriented Programming: Inheritance

Question 1

A method must be declared __________ for it to be overridden by derived classes.

A)Overrides
B)Overridable
C)Virtual
D)None of the above

Answer 1

Overridable

Question 2

All classes in Visual Basic have Object as either a direct or indirect base class.

Answer 2

True

Question 3

Which of the following pairs demonstrates the "is-a" relationship?

A)car,engine
B)book,table of contents
C)baseball,sport
D)None of the above

Answer 3

C

Question 4

To avoid duplicating code (and possibly errors),use ________,rather than ________.

A)inheritance,the "copy-and-paste" approach
B)the "copy-and-paste" approach,inheritance
C)a class that explicitly extends Object,a class that does not extend Object
D)a class that does not extend Object, a class that explicitly extends Object

Question 5

__________ is a form of xe "code reuse"xe "software reuse"software reuse in which a new class is created quickly and easily by absorbing an existing class's members and customizing them with new or modified capabilities.

A)Interfacing
B)Inheritance
C)Encapsulating
D)Polymorphism

Question 6

A base class's constructors are inherited into its derived classes.

Question 7

Which of the following could be a base class for class Computer?

A)machine
B)hard-drive
C)software
D)keyboard

Question 8

An advantage of inheritance is that:

A)all methods can be inherited
B)all instance variables can be uniformly accessed by base classes and derived classes
C)Objects of a derived class can be treated as objects of their base class
D)None of the above.

Question 9

A base class may have only one derived class.

Question 10

A derived class can add its own instance variables,Shared variables,properties and methods,and it can customize methods and properties it inherits.

Question 11

Every class in Visual Basic except __________ extends an existing class.

A)Integer
B)Object
C)Type
D)Class

Question 12

A base class is more specific than its derived class and represents a more specialized group of objects.

Question 13

Inheritance is represented by a(n)_________ relationship.

A)"uses"
B)"is-a"
C)"has-a"
D)None of the above.

Question 14

Which of the following is not a base/derived class relationship?

A)Ford/Taurus
B)University/Boston University
C)Sailboat/Tugboat
D)Country/USA

Question 15

When creating a class,rather than declaring completely new members,you can designate that the new class inherits the members of an existing class.The existing class is called the __________ class,and the new class is the __________ class.

A)derived,base
B)root,child
C)sub,super
D)base,derived

Question 16

A class inherited from two or more levels up in the hierarchy is known as a(n) .

A)indirect base class
B)direct base class
C)superclass
D)None of the above

Question 17

The default implementation of method ToString of Object returns a String representing ________.

A)the object's type
B)the object class name
C)namespace_name.object_class_name
D)None of the above

Question 18

Polymorphism enables you to conveniently xe "program in the general"program "in the general" rather than "xe "program in the specific"in the specific."

Question 19

Which of the following pairs demonstrates the "has-a" relationship?

A)car,vehicle
B)house,window
C)teacher,person
D)None of the above

Question 20

The class hierarchy begins with class __________.

A)Object
B)Point
C)Root
D)Base

Question 21

When a program creates a derived-class object,the Object constructor is the last constructor called and the first whose body finishes executing.

Question 22

Polymorphism allows for specifics to be dealt with during:

A)execution
B)compilation
C)programming
D)debugging

Question 23

How can a derived class constructor ccall a base class constructor?

A)implicitly
B)explicitly
C)a and b
D)the derived class cannot call the base class constructor

Question 24

For which of the following would polymorphism not provide a clean solution?

A)A billing program where there is a variety of clients who are billed with different fee structures.
B)A maintenance log program where a variety of machine data is collected and maintenance schedules are produced for each machine based on the data collected.
C)A program to compute a 5% savings account interest for bank clients.
D)An IRS program that maintains information on a variety of taxpayers and determines who to audit based on criteria for classes of taxpayers.

Question 25

In practice,derived classes should depend only on the base-class services (that is,Private methods and properties)and not on the base-class data implementation.

Question 26

To call the base-class default constructor explicitly,the call to a base-class constructor must be the first statement in the derived-class-constructor definition.

Question 27

Which statement is true when a base class has Protected instance variables?

A)A derived class object can assign an invalid value to the base class's Protected instance variables.
B)Derived class methods can depend on the base class's Protected data implementation.
C)Derived classes would need to be modified if the base class's Protected data implementation changes.
D)All of the above.

Question 28

When a derived-class member overrides a base-class member,the base-class member can be accessed from the derived-class by using the Visual Basic keyword .

A)MyBase
B)Top
C)Super
D)None of the above

Question 29

When a request is made to use a derived-class-object method through a base-class reference,Visual Basic polymorphically chooses the correct overridden method in the derived class that is associated with the object.

Question 30

Polymorphism involves:

A)the same message sent to a variety of objects of types related by inheritance
B)a specific message sent to each specific object
C)different messages sent to one object
D)None of the above.

Question 31

The first task of any base class's constructor is to call its derived class's constructor.

Question 32

With Protected instance variables in the base class,all the derived classes of the base class may need to be modified if the base-class implementation changes.In such a case,the software is said to be non-modifiable,because a small change in the base class can "break" derived-class implementations.

Question 33

Polymorphism allows the addition of classes providing they were at least considered during program development.

Question 34

Consider the classes below:
Which of the statements below is false?

A)Both variables a and b are instance variables.
B)After the constructor for Class B executes,the variable a will have the value 7.
C)After the constructor for Class B executes,the variable b will have the value 8.
D)A reference to an object of Class A can be treated as a reference to an object of Class B.

Question 35

When a base class method is overridden in a derived class,it is common to have the derived class version call the base class version and then do some additional work.

Question 36

Base class methods with this level of access cannot be called from derived classes.

A)Private
B)Public
C)Protected
D)None of the above

Question 37

A base class's method that's overridden in a derived class will be executed implicitly when the derived class's method is called.

Question 38

The Protected members of a base class may be accessed in their class or any classes derived from that base class.

Question 39

When a derived class constructor calls its base class constructor,what happens if the base class's constructor does not assign a value to one of its instance variables?

A)a syntax error occurs
B)a compile-time error occurs
C)a run-time error occurs
D)the instance variables are initialized to their default values

Question 40

Private fields of a base class can be accessed in a derived class

A)by calling Private methods declared in the base class
B)by calling Public or Protected methods declared in the base class
C)directly
D)All of the above

Question 41

An abstract class cannot have instance data and non-abstract methods.

Question 42

Classes which may be instantiated are ___________ classes.

A)instance
B)concrete
C)abstract
D)None of the above

Question 43

Abstract methods and properties do not provide an implementation.

Question 44

The use of polymorphism helps promote software extensibility.

Question 45

All methods in an abstract class are abstract.

Question 46

Which answer best describes how many interfaces a class can implement?

A)0
B)1
C)1 or more
D)0 or more

Question 47

You may define implementations for abstract methods to act as a default.

Question 48

The MustOverride keyword has the same effect as the Overridable keyword.

Question 49

Assigning a derived class reference to a base class variable is safe:

A)because the derived class has an object of its base class.
B)because the derived class is an object of its base class.
C)only when the base class is abstract.
D)only when the base class is concrete.

Question 50

Objects of abstract base classes can be instantiated.

Question 51

Concrete classes provide implementations for at least one of the methods and properties they define.

Question 52

Abstract classes are classes which may not be:

A)inherited
B)accessed by derived-classes
C)instantiated
D)None of the above.

Question 53

Which of the following statements about MustInherit base classes is true?

A)MustInherit base classes may contain data.
B)MustInherit base classes may not contain implementations of methods.
C)MustInherit base classes must declare all methods as MustOverride.
D)MustInherit base classes must declare all data members not given values as MustOverride.

Question 54

Once a class implements an interface,all objects of that class have a(n)__________ relationship with the interface type.

A)has a
B)equals
C)is a
D)composition

Question 55

Consider the MustInherit base classes below:
Any concrete subclass that inherits class Foo:

A)Must implement a method called Calculate.
B)Will not be able to access the instance variable a.
C)Will not be able to instantiate an object of class Foo.
D)All of the above.

Question 56

A class with MustOverride methods does not necessarily have to be a MustInherit class.

Question 57

Attempting to instantiate an object of an abstract class is a logic error.

Question 58

The _________ keyword is used to define methods within a MustInherit class that must be implemented in a derived class for that derived class to be concrete.

A)Overridable
B)Abstract
C)MustOverride
D)MustImplement.

Question 59

Polymorphism allows you to command a wide variety of objects of types related by inheritance as long as you know the objects' types.

Question 60

The ________ keyword is used to create an abstract class.

A)Polymorph
B)Inherit
C)Abstract
D)MustInherit

Question 61

An interface reference may invoke only the methods that the interface declares.

Question 62

All objects of a class are guaranteed to provide the functionality described by any interface that the class implements.

Question 63

A class that implements an interface must define all methods and properties of that interface.

Question 64

The UML distinguishes an interface from other classes by placing the word "interface" in__________ above the interface name.

A)italics
B)carets
C)guillemets
D)bold

Question 65

An interface may not provide properties with Get and Set accessors.

Question 66

Declaring an interface Protected allows for extra security precautions.

Question 67

By convention,the name for a Car interface is:

A)InterfaceCar
B)ICar
C)CarI
D)None of the above.

Question 68

A(n)________ is particularly appropriate for providing services that disparate objects have in common.

A)abstract class
B)concrete class
C)interface
D)None of the above.

Question 69

To use an interface,a class must define only the methods in the interface that it will need to use.

Question 70

An interface is typically used in place of a MustInherit class when there is no default implementation to inherit.

Question 71

Which is used to specify that a class will be implementing an interface?

A)Using
B):
C)Implements
D)Extends.

Question 72

If a class leaves one method in an interface undeclared,the class is implicitly declared by Visual Basic as a MustInherit class.

Question 73

A class that implements an interface but does not declare all of the interface's methods must be declared:

A)Public
B)Interface
C)MustInherit
D)Final

Question 74

The purpose of an interface is to:

A)provide similar objects with the same functionality,even though each will implement the functionality differently
B)provide different objects with the same functionality,even though each will implement the functionality differently
C)provide default implementations of methods and properties
D)None of the above.

Question 75

Which of the following does not complete the sentence correctly?
An interface _____________.

A)forces classes that implement it to declare all the interface methods.
B)is used in place of an MustInherit class when there is no default implementation to inherit.
C)cannot be instantiated.
D)can be instantiated.

Question 76

An interface is defined with keyword _________.

A)Interface
B)MustInherit
C)Implements
D)Abstract

Question 77

Which of the following properties could exist in an interface for files,cats and houses?

A)door
B)tail
C)age
D)None of the above.

Question 78

Interfaces can have__________ methods.

A)0
B)1
C)2
D)any number of

Question 79

Objects of unrelated classes that implement the same interface can respond to the method calls of that interface polymorphically.

Question 80

A class that implements an interface may not act as a base class for other classes.