Cis166 final review

CIS-166 Final
Open book, open notes, open computer
100 points
True/false, multiple choice, fill-in, short answer
Emphasis on material since midterm

Object Terminology Review
Object - like a noun, a thing
An object is based on a class
Properties - like an adjective, characteristics of object
Methods - like a verb, an action or behavior, something the object can do
Events - object response to user action or other events

Polymorphism
Overloading: Argument type determines which version of a method is used
Example: MessageBox.Show method
Overriding: Refers to a class that has the same method name as its base class
Method in subclass takes precedence

Specifying a Namespace
Namespaces are used in .Net to organize classes and source files
When referring to classes in a different namespace
Write out the entire namespace
Add an Imports Statement to include the namespace
Public Class Form1 Inherits System.Windows.Forms.Form Name of the Class Namespace

Instance versus Shared Variables
Instance variables or properties use a separate memory location for each instance of the object
Shared variables or properties use a single memory location that is available for ALL objects of a class
Can be accessed without instantiating an object of the class
Use the Shared keyword to create
Shared Methods can also be created

Constructors and Destructors
Constructor: Method that automatically executes when an object is instantiated
Create by writing a Public Sub New procedure
Destructor: Method that automatically executes when an object is destroyed
Create by writing a Finalize procedure

Collections
Group of objects
Can be strongly typed: all objects based on the same class
Similar to an array
Collection expands and contracts automatically
Have common properties and methods
Add, Remove, Count, Item

Item Property
Typically set as default property for a collection
Returns a member of the group
Typically based on an Index
Data type depends on the type of objects the collection manages

Text Data Files
Actual data stored in files on disk device
File ==> Entire collection of data of data
Records ==> Rows or lines, one per entity
Fields ==> Data elements within row

Text File Handling
A Stream is designed to transfer a series of bytes from one location to another
Streams are objects that have properties and methods
Found in the System.IO namespace
File handling projects usually contain an Imports statement before the statement declaring the form's class

Writing Data Files
Declare a new StreamWriter object
Use StreamWriter's WriteLine method
Call StreamWriter's Close method

Write and WriteLine Methods
Write Method: Places items consecutively in the file with no separator
WriteLine Method: Places an Enter (carriage return) between records

Reading Files
Declare a new StreamReader object
File must exist!
Use StreamReader's ReadLine method
Loop to retrieve multiple records
Call StreamReader's Close method

ReadLine Method
Use to read previously saved data
Each time it executes, it reads the next line of data
Always assign the value from the read to a location, such as a label, text box, or string variable

Checking for End of File
Use StreamReader's Peek Method
Peek looks at the next element without actually reading it
If you Peek beyond the last element the value returned is -1

Cis166 final review

by Randy Riness @ South Puget Sound Community College

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