Wrap-Up

Answers to Self Review Exercises

4.1

a) object. b) class. c) new. d) type, name. e) global namespace. f) instance variable. g) float, double, decimal. h) double-precision. i) ToDecimal. j) access modifier. k) void. l) ReadLine. m) using directive. n) single-precision. o) C. p) value, reference.

4.2

a) False. By convention, method names begin with an uppercase first letter and all subsequent words in the name begin with a capital first letter. b) False. A property's get accessor enables a client to retrieve the value of the instance variable associated with the property. A property's set accessor enables a client to modify the value of the instance variable associated with the property. c) True. d) True. e) False. After defining a property, you can use it the same way you use a variable. f) True. g) False. Such variables are called local variables and can be used only in the method in which they are declared. h) False. A property declaration can contain a get accessor, a set accessor or both. i) True. j) False. Instance variables are initialized by default. k) True. l) True. m) True. n) False. Such literals are of type double by default.

4.3

A local variable is declared in the body of a method and can be used only from the point at which it is declared through the end of the method declaration. An instance variable is declared in a class, but not in the body of any of the class's methods. Every object (instance) of a class has a separate copy of the class's instance variables. Also, instance variables are accessible to all methods of the class. (We will see an exception to this in Chapter 9, Classes and Objects: A Deeper Look.)

4.4

A parameter represents additional information that a method requires to perform its task. Each parameter required by a method is specified in the method's declaration. An argument is the actual value that is passed to a method parameter when a method is called.

Exercises

4.5

What is the purpose of operator new? Explain what happens when this keyword is used in an application.

4.6

What is a default constructor? How are an object's instance variables initialized if a class has only a default constructor?

4.7

Explain the purpose of an instance variable.

4.8

Explain how an application could use class Console without using a using directive.

4.9

Explain why a class might provide a property for an instance variable.

4.10

Modify class GradeBook (Fig. 4.12) as follows:

  1. Include a second string instance variable that represents the name of the course's instructor.
  2. Provide a property with accessors to change the instructor's name and to retrieve it.
  3. Modify the constructor to specify two parametersone for the course name and one for the instructor's name.
  4. Modify method DisplayMessage such that it first outputs the welcome message and course name, then outputs "This course is presented by: ", followed by the instructor's name.

Use your modified class in a test application that demonstrates the class's new capabilities.

4.11

Modify class Account (Fig. 4.15) to provide a method called Debit that withdraws money from an Account. Ensure that the debit amount does not exceed the Account's balance. If it does, the balance should be left unchanged and the method should print a message indicating "Debit amount exceeded account balance." Modify class AccountTest (Fig. 4.16) to test method Debit.

4.12

Create a class called Invoice that a hardware store might use to represent an invoice for an item sold at the store. An Invoice should include four pieces of information as instance variablesa part number (type string), a part description (type string), a quantity of the item being purchased (type int) and a price per item (decimal). Your class should have a constructor that initializes the four instance variables. Provide a property with a get and set accessor for each instance variable. In addition, provide a method named GetInvoiceAmount that calculates the invoice amount (i.e., multiplies the quantity by the price per item), then returns the amount as a decimal value. If the quantity is negative, it should be left unchanged. Similarly, if the price per item is negative, it should be left unchanged. Write a test application named InvoiceTest that demonstrates class Invoice's capabilities.

4.13

Create a class called Employee that includes three pieces of information as instance variablesa first name (type string), a last name (type string) and a monthly salary (decimal). Your class should have a constructor that initializes the three instance variables. Provide a property with a get and set accessor for each instance variable. If the monthly salary is negative, the set accessor should leave the instance variable unchanged. Write a test application named EmployeeTest that demonstrates class Employee's capabilities. Create two Employee objects and display each object's yearly salary. Then give each Employee a 10% raise and display each Employee's yearly salary again.

4.14

Create a class called Date that includes three pieces of information as instance variablesa month (type int), a day (type int) and a year (type int). Your class should have a constructor that initializes the three instance variables and assumes that the values provided are correct. Provide a property with a get and set accessor for each instance variable. Provide a method DisplayDate that displays the month, day and year separated by forward slashes (/). Write a test application named DateTest that demonstrates class Date's capabilities.

Control Statements Part 1

Preface

Index

    Introduction to Computers, the Internet and Visual C#

    Introduction to the Visual C# 2005 Express Edition IDE

    Introduction to C# Applications

    Introduction to Classes and Objects

    Control Statements: Part 1

    Control Statements: Part 2

    Methods: A Deeper Look

    Arrays

    Classes and Objects: A Deeper Look

    Object-Oriented Programming: Inheritance

    Polymorphism, Interfaces & Operator Overloading

    Exception Handling

    Graphical User Interface Concepts: Part 1

    Graphical User Interface Concepts: Part 2

    Multithreading

    Strings, Characters and Regular Expressions

    Graphics and Multimedia

    Files and Streams

    Extensible Markup Language (XML)

    Database, SQL and ADO.NET

    ASP.NET 2.0, Web Forms and Web Controls

    Web Services

    Networking: Streams-Based Sockets and Datagrams

    Searching and Sorting

    Data Structures

    Generics

    Collections

    Appendix A. Operator Precedence Chart

    Appendix B. Number Systems

    Appendix C. Using the Visual Studio 2005 Debugger

    Appendix D. ASCII Character Set

    Appendix E. Unicode®

    Appendix F. Introduction to XHTML: Part 1

    Appendix G. Introduction to XHTML: Part 2

    Appendix H. HTML/XHTML Special Characters

    Appendix I. HTML/XHTML Colors

    Appendix J. ATM Case Study Code

    Appendix K. UML 2: Additional Diagram Types

    Appendix L. Simple Types

    Index



    Visual C# How to Program
    Visual C# 2005 How to Program (2nd Edition)
    ISBN: 0131525239
    EAN: 2147483647
    Year: 2004
    Pages: 600

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