Programming Right From the Start with Visual Basic.NET
CHAPTER 14
Advanced Object-Oriented Programming
True-False Questions
1.
2.
3.
4.
5.
Objects have properties.
Answer: True
Section: 14-1
Level: Easy
Page: 390
Properties have methods.
Answer: False
Section: 14-1
Level: Easy
Page: 390
All Controls are objects.
Answer: True
Section: 14-1
Level: Easy
Page: 390
All Objects are controls.
Answer: False
Section: 14-1
Level: Easy
Page: 390
Classes and objects are really the same thing.
Answer: False
Section: 14-1
Level: Moderate
Page: 391
6.
Actions and data that are grouped together are called objects.
Answer: True
Level: Easy
Section: 14-1
Page: 391
7.
The design of an object is called a class.
Answer: True
Section: 14-1
Level: Moderate
Page: 391
A property is the action associated with an object.
Answer: False
Section: 14-1
Level: Moderate
Page: 391
One class can create many objects.
Answer: True
Section: 14-1
Level: Moderate
Page: 391
A class is an instance of an object.
Answer: False
Section: 14-1
Level: Hard
Page: 391
8.
9.
10.
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Chapter 14 – Advanced Object-Oriented Programming
11.
Object oriented programming is considered just one way to deal with the inherent complexity of
software development.
Answer: True
Level: Moderate
Section: 14-2
Page: 391
12.
The prefix for a class is T, which stands for text.
Answer: False
Section: 14-2
Level: Moderate
Page: 392
13.
One advantage of encapsulation is that it protects data in an object from external code.
Answer: True
Level: Moderate
Section: 14-2
Page: 392
14.
To ensure proper encapsulation internal variables are declared as public.
Answer: False
Level: Moderate
Section: 14-2
Page: 392
15.
Always use properties to encapsulate data.
Answer: True
Section: 14-2
Level: Moderate
Page: 392
16.
Only some properties and methods are inherited from a base class.
Answer: False
Level: Moderate
Section: 14-2
Page: 392
17.
Inheritance makes it easy to reuse existing code in new applications.
Answer: True
Level: Easy
Section: 14-2
Page: 392
18.
Making a change in a base class will always cause the derived class to change.
Answer: True
Level: Easy
Section: 14-2
Page: 392
19.
New properties can not be added to a derived class.
Answer: False
Section: 14-2
Level: Moderate
Page: 392
20.
Polymorphism means that one method can have many names.
Answer: False
Level: Hard
Section: 14-2
Page: 393
21.
The fact that multiplication can apply to a variety of data types is an example of polymorphism.
Answer: True
Level: Moderate
Section: 14-2
Page: 393
22.
The two parts of a class definition are properties and methods.
Answer: False
Level: Moderate
Section: 14-3
Page: 393
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Chapter 14 – Advanced Object-Oriented Programming
23.
A property is a privately defined variable in a class.
Answer: False
Section: 14-3
Level: Moderate
Page: 393
24.
A class method can be either a function procedure or a sub procedure.
Answer: True
Level: Moderate
Section: 14-3
Page: 393
25.
When a constructor is called, it means a new object is created.
Answer: True
Level: Easy
Section: 14-3
Page: 393
26.
It is best to define a field as a private variable.
Answer: True
Section: 14-3
Level: Easy
Page: 394
27.
A field should have a prefix of P, which stands for private.
Answer: False
Level: Easy
Section: 14-3
Page: 394
28.
The standard way to interact with a private field is to use a property.
Answer: True
Level: Easy
Section: 14-3
Page: 395
29.
The get procedure of a property is used to assign a value to field.
Answer: False
Level: Moderate
Section: 14-3
Page: 395
30.
The best way to make a property read only is to not put code in the Set procedure.
Answer: False
Level: Moderate
Section: 14-3
Page: 395
31.
A method in a class can only be defined as Public.
Answer: False
Section: 14-3
Level: Moderate
Page: 396
A method in a class can read any field in that class.
Answer: True
Section: 14-3
Level: Moderate
Page: 396
32.
33.
Having multiple constructors in a class is an example of polymorphism.
Answer: True
Level: Hard
Section: 14-3
Page: 397
34.
A constructor is a property that is used to create a new object.
Answer: False
Level: Moderate
Section: 14-3
Page: 397
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Chapter 14 – Advanced Object-Oriented Programming
35.
The code to call the constructor of a base class is MyBaseClass.New().
Answer: False
Level: Moderate
Section: 14-3
Page: 397
36.
Parameters are required in a call to a constructor.
Answer: False
Section: 14-3
Level: Moderate
Page: 397
Multiple Choice Questions
37.
Which control is an example of an object in VB.NET?
a.) Button
b.) Label
c.) Textbox
d.) Both a and b.
e.) All of the above.
Answer: e
Section: 14-1
38.
Level: Easy
Page: 390
Which of the following is part of an object?
a.) Methods
b.) Properties
c.) Instances
d.) Both a and b.
e.) All of the above.
Answer: d
Section: 14-1
39.
Level: Moderate
Page: 390
Which is true about objects?
a.) Objects are used to create classes.
b.) Objects are analogous to blueprints.
c.) Objects combine actions and data.
d.) Both a and b.
e.) All of the above.
Answer: c
Section: 14-1
Level: Moderate
Page: 391
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Chapter 14 – Advanced Object-Oriented Programming
40.
Properties are used to represent:
a.) actions.
b.) classes.
c.) data.
d.) events.
e.) instances.
Answer: c
Section: 14-1
41.
Level: Easy
Page: 391
Methods are used to represent:
a.) actions.
b.) classes.
c.) data.
d.) events.
e.) instances.
Answer: a
Section: 14-1
42.
Level: Easy
Page: 391
The term instantiation refers to the creation of:
a.) a class from a blueprint.
b.) an object from a class.
c.) a method from an object.
d.) a property from a method.
e.) a blueprint from a property.
Answer: b
Section: 14-1
43.
Level: Moderate
Page: 391
Anything in VB.NET that has a property or method is:
a.) a class.
b.) a control.
c.) an object.
d.) Both a and b.
e.) All of the above.
Answer: c
Section: 14-1
44.
Level: Moderate
Page: 391
Which feature is needed to make a programming language object oriented?
a.) Encapsulation
b.) Inheritance
c.) Polymorphism
d.) Both a and b.
e.) All of the above.
Answer: e
Section: 14-2
Level: Easy
Page: 391
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Chapter 14 – Advanced Object-Oriented Programming
45.
We should think of the practice of object-oriented programming as:
a.) a simple answer to the complex problem of creating software.
b.) an incremental improvement to the problem of creating software.
c.) the way to get rid of a werewolf.
d.) Both a and b.
e.) All of the above.
Answer: b
Section: 14-2
46.
Level: Moderate
Page: 391
Encapsulation makes it easier to:
a.) reuse and modify existing modules of code.
b.) write and read code by sharing method names.
c.) hide and protect data from external code.
d.) Both a and b.
e.) All of the above.
Answer: c
Section: 14-2
47.
Level: Moderate
Page: 392
Inheritance makes it easier to:
a.) reuse and modify existing modules of code.
b.) write and read code by sharing method names.
c.) hide and protect data from external code.
d.) Both a and b.
e.) All of the above.
Answer: a
Section: 14-2
48.
Level: Moderate
Page: 392
Polymorphism makes it easier to:
a.) reuse and modify existing modules of code.
b.) write and read code by sharing method names.
c.) hide and protect data from external code.
d.) Both a and b.
e.) All of the above.
Answer: b
Section: 14-2
49.
Level: Moderate
Page: 393
The standard prefix to signify a class is:
a.) B.
b.) C.
c.) L.
d.) S.
e.) T.
Answer: e
Section: 14-2
Level: Moderate
Page: 392
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Chapter 14 – Advanced Object-Oriented Programming
50.
When using encapsulation how should data be shared with external code?
a.) Events
b.) Methods
c.) Properties
d.) Private variables
e.) Public variables
Answer: c
Section: 14-2
51.
Level: Moderate
Page: 392
Which statement is true?
a.) A base class inherits some of the properties of a derived class.
b.) A base class inherits all of the properties of a derived class.
c.) A derived class inherits some of the properties of a base class.
d.) A derived class inherits all of the properties of a base class.
e.) None of the above.
Answer: d
Section: 14-2
52.
Level: Moderate
Page: 392
When a base class is changed:
a.) there is no effect on the derived class.
b.) the derived class changes when the key word Overridden is used.
c.) only the methods of the derived class change.
d.) only the properties of the derived class change.
e.) the derived class automatically changes.
Answer: e
Section: 14-2
53.
Level: Easy
Page: 392
Polymorphism can apply to:
a.) math operators.
b.) method names.
c.) object names.
d.) Both a and b.
e.) All of the above.
Answer: d
Section: 14-2
54.
Level: Moderate
Page: 393
With polymorphism:
a.) one method can have multiple names.
b.) one object can have multiple names.
c.) many methods can share the same name.
d.) many objects can share the same name.
e.) None of the above statements are true.
Answer: c
Section: 14-2
Level: Hard
Page: 393
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Chapter 14 – Advanced Object-Oriented Programming
55.
Which element of a class is optional?
a.) Constructs
b.) Fields
c.) Methods
d.) Properties
e.) All of the above.
Answer: e
Section: 14-3
56.
Level: Moderate
Page: 394
What is the suggested order for the definition of class elements from first to last?
a.) Constructs, fields, methods, properties
b.) Properties, constructs, fields, methods
c.) Fields, properties, constructs, methods
d.) Constructs, properties, fields, methods
e.) Methods, constructs, properties, fields
Answer: c
Section: 14-3
57.
Level: Hard
Page: 394
The standard for designing a field is that it be defined as a:
a.) private method.
b.) public method.
c.) private variable.
d.) public variable.
e.) None of the above.
Answer: c
Section: 14-3
58.
Level: Moderate
Page: 393
What is the syntax for making a property read-only?
a.) Property Read propertyname As datatype
b.) Read Property propertyname As datatype
c.) ReadOnly Property propertyname As datatype
d.) Read-Only Property propertyname As datatype
e.) RO Property propertyname As datatype
Answer: c
Section: 14-3
59.
Level: Moderate
Page: 395
The Get procedure of a property acts like:
a.) an event.
b.) a function.
c.) a variable.
d.) Both a and b.
e.) All of the above.
Answer: b
Section: 14-3
Level: Hard
Page: 395
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Chapter 14 – Advanced Object-Oriented Programming
60.
A method in a class is:
a.) a sub procedure.
b.) a function.
c.) an event.
d.) Both a and b.
e.) All of the above.
Answer: d
Section: 14-3
61.
Level: Moderate
Page: 396
How many constructors can a class have?
a.) 0
b.) 1
c.) 2
d.) 3
e.) All of the above.
Answer: e
Section: 14-3
62.
Level: Easy
Page: 397
A constructor is a special type of:
a.) class.
b.) field.
c.) method.
d.) property.
e.) variable.
Answer: c
Section: 14-3
63.
Level: Easy
Page: 397
Which is true for constructors in a class?
a.) All constructors must have the same number of parameters.
b.) All constructors must be the same parameter data type.
c.) Some constructors can have the same list of parameters.
d.) Only two constructors in a class can have the same list of parameters.
e.) No two constructors in a class can have the same list of parameters.
Answer: e
Section: 14-3
64.
Level: Moderate
Page: 397
Which statement will call a constructor of a base class?
a.) Base.New( )
b.) BaseConstructor.New ( )
c.) CallBase.New( )
d.) Constructor.New ( )
e.) MyBase.New( )
Answer: e
Section: 14-3
Level: Moderate
Page: 397
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Chapter 14 – Advanced Object-Oriented Programming
Fill in the Blank Questions
65.
The controls on a form and the form itself are examples of ___objects___.
Level: Easy
Section: 14-1
Page: 390
66.
The name and text of a textbox control are ___properties___ of the control.
Level: Moderate
Section: 14-1
Page: 390
67.
The ___class___ is similar to a blueprint for the object.
Level: Moderate
Section: 14-1
Page: 391
68.
Creating an object from a class is called ___instantiation___.
Level: Hard
Section: 14-1
Page: 391
69.
Elements in VB.NET that have methods and properties are considered ___objects___.
Level: Moderate
Section: 14-1
Page: 391
70.
The process of hiding the internal data and actions of an object is called ___encapsulation___.
Level: Easy
Section: 14-2
Page: 392
71.
Objects should always use ___properties___ to interact with external code.
Level: Moderate
Section: 14-2
Page: 392
72.
Internal methods and variables of an object should be declared ___private____.
Level: Moderate
Section: 14-2
Page: 392
73.
Creating modified and specialized versions of an existing class is called ___inheritance___.
Level: Moderate
Section: 14-2
Page: 392
74.
A(n) ___base___ class is used to create a derived class.
Level: Moderate
Section: 14-2
Page: 392
75.
When a method in a derived class is modified, it is called a(n) ___overridden___ method.
Level: Moderate
Section: 14-2
Page: 392
76.
Changes in a ___base___ class will propagate to all derived classes.
Level: Moderate
Section: 14-2
Page: 392
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Chapter 14 – Advanced Object-Oriented Programming
77.
The capacity to have different methods all using the same name is called ___polymorphism___.
Level: Moderate
Section: 14-2
Page: 393
78.
A single math operator can apply to different sets of data types is an example of
___polymorphism___.
Level: Moderate
Section: 14-2
Page: 393
79.
A private variable is a class called a ___field___.
Level: Easy
Section: 14-3
Page: 393
80.
Making a field in a class private helps to ensure ___data hiding___.
Level: Hard
Section: 14-3
Page: 394
81.
The ___fields___ of a class should be defined first.
Level: Moderate
Section: 14-3
Page: 394
82.
The ___Get___ procedure of a property is used to output data from an object.
Level: Hard
Section: 14-3
Page: 395
83.
The ___Set___ procedure of a property is used for data input into an object.
Level: Hard
Section: 14-3
Page: 395
84.
___Properties___ are used to access private fields in an object.
Level: Moderate
Section: 14-3
Page: 395
85.
You can prevent external code from changing the value of a property by using the
___ReadOnly___ keyword to define the property.
Level: Moderate
Section: 14-3
Page: 395
86.
Procedures defined in a class are called ___methods___.
Level: Easy
Section: 14-3
Page: 396
87.
A method of an object can be either a sub or ___function___.
Level: Moderate
Section: 14-3
Page: 396
88.
Every constructor of an object is named ___New___.
Level: Moderate
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Chapter 14 – Advanced Object-Oriented Programming
Section: 14-3
89.
Page: 397
A derived class uses ___MyBase.New( )___ to call the constructor of its parent class.
Level: Hard
Section: 14-3
Page: 397
Essay Questions
90.
Describe the three main features of an object-oriented programming language.
An object-oriented programming language will have encapsulation, inheritance, and
polymorphism.
Encapsulation is the process of making an object into a secure module with hidden data. An
encapsulated object will have public properties to allow limited access to information internal to
the object. Only methods needed by external code will be declared as public, all other methods
will be private. This decreases the ability of external code to change the objects internal
variables, either by accident or design. A standard interface for interacting with an object also
means that modifications can be made to the internal workings of the object without having to
make modifications to the code that uses the object. This decreases the cost of maintaining
software.
Inheritance is the ability to take an existing object with all of its methods and properties and
create newer, improved versions by adding or overriding properties and methods. This decrease
the time it takes to create new objects because existing functions that work well can be reused. A
programmer can reuse the button control that already exists instead of writing a new version of
the button control. They can also make a derived button class that will have unique properties
designed for their application. One advantage of inheritance is that modifications in the base
class will automatically propagate to all the derived classes.
Polymorphism allows objects to have multiple methods that share the same name. This allows a
group of related methods to perform similar functions but with different types of input. Each
version of the method must have a unique parameter signature (list). One example would be
multiple versions of a Print method that can print to the screen any type of variable (string,
integer, decimal, …). Without polymorphism each data type would need its own print method
such as Print_integer, Print_string, Print_decimal. This greatly simplifies the job of a
programmer and makes the code easier to read and write.
91.
What is a constructor? How is it used in a class?
A constructor is a method that is called every time a new instance of an object is created. It fills
the properties of an object when it is first instantiated.
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Chapter 14 – Advanced Object-Oriented Programming
All constructors for a class are named New (this is an example of polymorphism). If no specific
constructor is requested, the constructor with no parameters is called, New( ). However a class
can have no constructors at all.
Derived classes can call the constructors of the parent or base class by using the keyword
MyBase, as with the code below.
MyBase.New(“Joe”, “Smith”, “777-7777”)
14 - 13