murach’s visual basic 2008, modified, c8© 2008, mike murach & associates, inc. slide 1

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Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 1

1How to Declare and Instantiate an ArrayMurachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 2Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 3

3What if you do not know the size needed?Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 4Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 5

5Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 6




9How to reference the elements of an array?Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 10Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 11







17To Enhance Your UnderstandingRead pp. 223-229Do Exercise 8-1 #1-3Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 18Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 19



21To Enhance Your UnderstandingRead pp. 223-231Do Exercise 8-1 #1-7Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 22Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 23

Syntax for Rectangular Arrays23Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 24





28To Enhance Your UnderstandingRead pp. 223-235Do Exercise 8-2Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 29Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 30



























56To Enhance your Learning:Read pp. 252-253Do Exercise 8-1, # 9 & 10Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 57The SortedList() ClassUses a key to access each elementInefficient for sequential accessEfficient for insertinf elements into the listSorted key order maintained automaticallyMurachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 58KeyValuePair StructureTwo PropertiesKeyValue Value can storeValue type orReference type

Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 59Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 60





64Lab AssignmentCreate a project that will test the code on p. 255Create a form with an appropriate interface to work with the code.Allow the user to enter key value pairs on the form.Allow the user to specify for whom they wish to search.Allow the user to request a display of the data.Test the code only. Do not worry about validating data, etc.Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 65Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 66


67Lab Assignment, QueueCreate a project that will test the code on p. 257Create a form with an appropriate interface to work with the code.Allow the user to enter names to put in the queue.Allow the user to specify for whom they wish to search (code not supplied).Allow the user to request a display of the names in the queue.Test the code only. Do not worry about validating data, etc.

Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 68Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 69


70ArrayListIs an Untyped collection (legacy)Works mostly like a List()Is not on testMurachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 71Lab Assignment, StacksCreate a project that will test the code on p. 257Create a form with an appropriate interface to work with the code.Allow the user to enter names to put in the stack.Allow the user to specify for whom they wish to search (code not supplied).Allow the user to request a display of the names in the stack.Allow the user to peek.Test the code only. Do not worry about validating data, etc.

Murachs Visual Basic 2008, modified, C8 2008, Mike Murach & Associates, Inc.Slide 72Chapter 8

How to work with arrays and collections

Declaring and initializing a one-dimensional array

Dim arrayName(upperbound) As type

Index goes from 0 to upperbound.

Array length or size is upperbound + 1.ExampleDim numbers(3) As Integer

Declaring but not initializing a one-dimensional arrayDim arrayName() As type

Example

Dim totals() As Decimal

Initializing an array that has only been declaredarrayName = New type(upperbound) {}

Example

Dim totals() As Decimal

totals = New Decimal(49) {}

Getting the upper bound from a variableDim maxTotals As Integer = CInt(txtUpperBound.Text)

Dim totals(maxTotals) As DecimalUsing the New keyword to initialize an array

Dim maxTotals As Integer = CInt(txtUpperBound.Text)

Dim totals() As Decimaltotals = New Decimal(maxTotals) {}

How to document the lower bound when you declare an array

Dim titles(0 To 49) As String ' provides for 50 titles

Default values for array elements

Data typeDefault value

All numeric types0 (zero)

CharNull (binary 0)

BooleanFalse

Date01/01/0001 00:00:00

All reference typesNull reference

The syntax for referring to an element of an array

arrayName(index)Code that assigns values to an array of Decimal types

Dim totals(3) As Decimal ' this provides for 4 elements

totals(0) = 14.95D

totals(1) = 12.95D

totals(2) = 11.95D

totals(3) = 9.95D

'totals(4) = 8.95D

' this would throw an IndexOutOfRangeException

Code that assigns objects to an array of strings

Dim names(2) As String

names(0) = "Ted Lewis"

names(1) = "Sue Jones"

names(2) = "Ray Thomas"

The syntax for creating an array and assigning values in one statement

Dim arrayName() As type = [New type(upperbound)] {value1[, value2]

[, value3]...}

Examples

Dim totals() As Decimal = {14.95D, 12.95D, 11.95D, 9.95D}

Dim names() as String =

{"Ted Lewis", "Sue Jones", "Ray Thomas"}

Dim totals() As Decimal =

New Decimal(3) {14.95D, 12.95D, 11.95D, 9.95D}

The syntax for using the Length property of an array

arrayName.Length

A For loop that puts the numbers 0 through 9 into an array Fill the array.Dim numbers(9) As Integer

For i As Integer = 0 To numbers.Length - 1

numbers(i) = i

Next

Code that displays the numbers array in a message box

Dim numbersString As String = ""

For i As Integer = 0 To numbers.Length - 1

numbersString &= numbers(i).ToString & " "

Next

MessageBox.Show(numbersString, "Numbers Test")

The message box thats displayed

Code that uses a For loop to compute the average of a totals array

Dim totals() As Decimal = {14.95D, 12.95D, 11.95D, 9.95D}

Dim sum As Decimal = 0

For i As Integer = 0 To totals.Length - 1

sum += totals(i)

Next

Dim average As Decimal = sum / totals.Length

Code that displays the totals array in a message box

Dim totalsString As String = ""

For i As Integer = 0 To totals.Length - 1

totalsString &= total.ToString & vbCrLf

Next

MessageBox.Show("The totals are:" _

& vbCrLf & totalsString & vbCrLf & _

"Sum: " & sum & vbCrLf & "Average: " & average, _

"Totals Test")


The syntax of a For Each loop

For Each elementName [As type] In arrayName statements

Next



For Each number As Integer In numbers

numbersString &= number.ToString & " "Next



Code that computes the average of the totals array

Dim sum As Decimal = 0

For Each total As Decimal In totals

sum += total

Next

Dim average As Decimal = sum / totals.Length

Code that displays the totals array in a message box

Dim totalsString As String = ""

For Each total In totals

totalsString &= total.ToString & vbCrLf

Next

MessageBox.Show("The totals are:" _

& vbCrLf & totalsString & vbCrLf & _

"Sum: " & sum & vbCrLf & "Average: " & average, _

"Totals Test")


Declaring a rectangular array

Dim arrayName(firstupperbound, secondupperbound) As type

Example: Create a 3x2 array

Dim numbers(2,1) As Integer

Referring to an element of a rectangular array

arrayName(rowindex, columnindex)Code that assigns values to the numbers array

numbers(0,0) = 1

numbers(0,1) = 2

numbers(1,0) = 3

numbers(1,1) = 4

numbers(2,0) = 5

numbers(2,1) = 6

Code that creates a 3x2 array and assigns values with one statement

Dim numbers(,) As Integer = { {1,2}, {3,4}, {5,6} }

Code that creates and assigns values to a 3x2 array of strings

Dim products(,) As String = _

{{"VB08", "Murach's Visual Basic 2008"}, _

{"JSE6", "Murach's Java SE 6"}, _

{"A3VB", "Murach's ASP.NET 3.5 with VB 2008"}}

The syntax for using the GetLength method of a rectangular array

arrayName.GetLength(dimensionindex)

Code that works with the numbers array

Dim numbers(,) As Integer = { {1,2}, {3,4}, {5,6} }

Dim numberOfRows As Integer = numbers.GetLength(0)

Dim numberOfColumns As Integer = numbers.GetLength(1)

Dim sumOfFirstRow As Integer = numbers(0,0) _

+ numbers(0,1)

Displays the numbers array in a message box


For i As Integer = 0 To numbers.GetLength(0) - 1 For j As Integer = 0 To numbers.GetLength(1) - 1 numbersString &= numbers(i, j) & " "

Next

numbersString &= vbCrLf

Next



Displays the products array in a message box

Dim productsString As String = ""

For i As Integer = 0 To products.GetLength(0) 1 For j As Integer = 0 To products.GetLength(1) - 1

productsString &= products(i, j) & vbTab

Next j

productsString &= vbCrLf

Next iMessageBox.Show(productsString, "Products Test")


The syntax for declaring a jagged array

Dim arrayName(numberofrows)() As typeCode that declares a jagged array with three rows

Dim numbers (2)() As Integer numbers(0) = New Integer(2) {} numbers(1) = New Integer(3) {} numbers(2) = New Integer(1) {} The syntax for referring to an element of a jagged array

arrayName(rowindex)(columnindex)Statements that assign values to the numbers array

numbers(0)(0) = 1numbers(1)(0) = 4numbers(2)(0) = 8

numbers(0)(1) = 2numbers(1)(1) = 5numbers(2)(1) = 9

numbers(0)(2) = 3numbers(1)(2) = 6

numbers(1)(3) = 7

Code that creates the numbers array with one statement

Dim numbers()() As Integer = {New Integer() {1, 2, 3}, _

New Integer() {4, 5, 6, 7}, _

New Integer() {8, 9}}Code that creates a jagged array of stringsDim titles()() As String = _

{New String(2) {"War and Peace", "Wuthering Heights", _

"1984"}, _

New String(3) {"Casablanca", "Wizard of Oz", _

"Star Wars", "Birdy"}, _

New String(1) {"Blue Suede Shoes", "Yellow Submarine"}}



For i As Integer = 0 To numbers.GetLength(0) - 1

For j As Integer = 0 To numbers(i).Length - 1

numbersString &= numbers(i)(j) & " "

Next numbersString &= vbCrLf

NextMessageBox.Show(numbersString, "Jagged Numbers Test")


Code that displays the titles array in a message box


For i As Integer = 0 To titles.GetLength(0) - 1

For j As Integer = 0 To titles(i).Length - 1

numbersString &= titles(i)(j) & " "

Next j

numbersString &= vbCrLf

Next i

MessageBox.Show(numbersString, "Jagged Titles Test")


Common properties and methods of the Array class

PropertyDescription

LengthGets the number of elements in all of the dimensions of an array.

Instance methodDescription

GetLength(dimension)Gets the number of elements in the specified dimension of an array.

GetUpperBound(dimension)Gets the index of the last element in the specified dimension of an array.

Common properties and methods of the Array class (continued)Static methodDescription

Copy(array1, array2, length)Copies some or all of the values in one array to another array.

BinarySearch(array, value)Searches a one-dimensional array thats in ascending order for an element with a specified value and returns the index for that element.

Sort(array)Sorts the elements in a one-dimensional array into ascending order.

Code that uses the GetLength and GetUpperBound methods

Dim numbers() As Integer = {1, 2, 3, 4}Dim length As Integer = numbers.GetLength(0)Dim upperBound As Integer = numbers.GetUpperBound(0)Code that uses the Sort method

Dim lastNames() As String = {"Boehm", "Taylor", _

"Murach", "Vasquez"}

Array.Sort(lastNames)

Dim message As String = ""

For Each lastName As String In lastNames

message &= lastName & vbCrLf

Next

MessageBox.Show(message, "Sorted Last Names")


Code that uses the BinarySearch method

Dim employees() As String = {"Adams", "Finkle", _

"Lewis", "Potter"}

Dim salesAmounts() As Decimal = {3275.68D, 4298.55D, _

5289.57D, 1933.98D}

Dim index As Integer = Array.BinarySearch(employees, _

"Finkle")

Dim salesAmount As Decimal = salesAmounts(index)Code that creates a reference to another array

Dim inches1() As Double = {1, 2, 3}

Dim inches2() As Double = inches1

How to copy elements of one array to another array

The syntax for copying elements of an array

Array.Copy(fromarray, toarray, length)Another way to copy elements from one array to another

Array.Copy(fromarray, fromindex, toarray, toindex, length)Code that copies all the elements of an array

Dim inches() As Double = {1, 2, 3, 4}

Dim centimeters(3) As Double

Array.Copy(inches, centimeters, inches.Length)For i As Integer = 0 To centimeters.Length - 1

centimeters(i) *= 2.54NextCode that copies some of the elements of an array

Dim names() As String = {"Boehm", "Murach", "Vasquez"}

Dim lastTwoNames(1) As StringArray.Copy(names, 1, lastTwoNames, 0, 2)

How to return an array from a procedure

A Function procedure that returns an array

Private Function RateArray( _

ByVal elementCount As Integer) As Decimal()

Dim rates(elementCount - 1) As Decimal

For i As Integer = 0 To rates.Length - 1

rates(i) = (i + 1) / 100D

Next

Return rates

End Function

A statement that calls the procedure

Dim rates() As Decimal = Me.RateArray(4)

How to code a procedure that accepts an array argument

A Sub procedure that converts an array of inches to an array of centimeters

Private Sub ConvertToCentimeters( _

ByRef measurements() As Double)

For i As Integer = 0 To measurements.Length - 1

measurements(i) *= 2.54

Next

End Sub

Statements that declare an array and call the procedure

Dim measurements() As Double = {1, 2, 3}

Me.ConvertToCentimeters(measurements)

Arrays and Collections both can:

Store multiple elementsBe value types or reference types.

Differences:Class

An array inherits the Array class. Collections are other classes.

Different methodsSize

Arrays - fixed Collections -- variable

Commonly used collection classes

.NET 2.0 to 3.5.NET 1.xDescription

List()ArrayListUses an index to access each element. Efficient for accessing elements sequentially; inefficient for inserting elements into a list.

SortedList()SortedListUses a key to access a value, which can be any type of object. Efficient for inserting elements into a list; can be inefficient for accessing elements sequentially.

Queue()QueueUses special methods to add and remove elements.

Stack()StackUses special methods to add and remove elements.

Untyped collections: An example

Dim numbers As New ArrayListnumbers.Add(3)numbers.Add(70)

numbers.Add("Test")Dim sum As Integer = 0

Dim number As Integer

For i As Integer = 0 To numbers.Count - 1

number = CInt(numbers(i))

sum += number

Next

Typed collections: An example

Dim numbers As New List(Of Integer)numbers.Add(3)

numbers.Add(70)

'numbers("Test")Dim sum As Integer = 0

Dim number As IntegerFor i As Integer = 0 To numbers.Count - 1

number = numbers(i) sum += number

Next

A statement that creates a list of String elements

Dim titles As New List(Of String)

A statement that creates a list of Decimal elements

Dim prices As New List(Of Decimal)

A statement that creates a list of strings with a capacity of 3

Dim lastNames As New List(Of String)(3)

Common properties and methods of the List() class

PropertyDescription

Item(index)Gets or sets the element at the specified index. The index for the first item in a list is 0. Since Item is the default property, its name can be omitted.

CapacityGets or sets the number of elements the list can hold.

CountGets the number of elements in the list.

MethodDescription

Add(object)Adds an element to the end of a list and returns the elements index.

Clear()Removes all elements from the list and sets its Count property to zero.

Common properties and methods of the List() class (continued)

MethodDescription

Contains(object)Returns a Boolean value that indicates if the list contains the specified object.

Insert(index, object)Inserts an element into a list at the specified index.

Remove(object)Removes the first occurrence of the specified object from the list.

RemoveAt(index)Removes the element at the specified index of a list.

BinarySearch(object)Searches a list for a specified object and returns the index for that object.

Sort()Sorts the elements in a list into ascending order.

Code that causes the size of the list of names to be increased

Dim lastNames As New List(Of String)(3) ' capacity is 3 elements

lastNames.Add("Boehm")

lastNames.Add("Prince")

lastNames.Add("Murach")

lastNames.Add("Taylor") ' capacity is doubled to 6 elementslastNames.Add("Vasquez")

lastNames.Add("Steelman")

lastNames.Add("Slivkoff") ' capacity is doubled to 12 elements

The syntax for retrieving a value from a list

listName[.Item](index)Code that creates a list that holds Decimal values

Dim newSalesTotals() As Decimal = {3275.68D, 4398.55D, _

5289.75D, 1933.98D}

Dim salesTotals As New List(Of Decimal)

For Each d As Decimal In newSalesTotals

salesTotals.Add(d)

Next

Code that retrieves the first value from the list

Dim sales1 As Decimal = salesTotals(0) ' sales1 = 3275.68Code that inserts and removes an element from the list

salesTotals.Insert(0, 2745.73D) sales1 = salesTotals(0) Dim sales2 As Decimal = salesTotals(1)

salesTotals.RemoveAt(1) sales2 = salesTotals(1)

Code that displays the list in a message box

Dim salesTotalsString As String = ""

For Each d As Decimal In salesTotals

salesTotalsString &= d.ToString & vbCrLf

Next

MessageBox.Show(salesTotalsString, "Sales Totals")


Code that checks for an element in the list and removes it if it exists

Dim x As Decimal = 2745.73D

If salesTotals.Contains(x) Then

salesTotals.Remove(x)

End IfCode that sorts and searches the list

salesTotals.Sort()

Dim sales2Index As Integer = _

salesTotals.BinarySearch(sales2)' sales2Index = 1Common properties of the SortedList() class

PropertyDescription

Item(key)Gets or sets the value of the element with the specified key. Since Item is the default property, its name can be omitted.

KeysGets a collection that contains the keys in the list.ValuesGets a collection that contains the values in the list.

CapacityGets or sets the number of elements the list can hold.

CountGives the number of elements in the list.

Common methods of the SortedList() class

MethodDescription

Add(key, value)Adds an element with the specified key and value to the sorted list.

Clear()Removes all elements from the sorted list.

ContainsKey(key)Returns a Boolean value that indicates whether or not the sorted list contains the specified key.

ContainsValue(value)Returns a Boolean value that indicates whether or not the sorted list contains the specified value.

Common methods of the SortedList() class (cont.)MethodDescription

Remove(key)Removes the element with the specified key from the sorted list.

RemoveAt(index)Removes the element at the specified index from the sorted list.

Properties of the KeyValuePair structure

PropertyDescription

KeyThe key for the SortedList item.

ValueThe value associated with the key.

Code that creates and loads a sorted list

Dim salesList As New SortedList(Of String, Decimal)

salesList.Add("Adams", 3274.68D)

salesList.Add("Finkle", 4398.55D)

salesList.Add("Lewis", 5289.75D)

salesList.Add("Potter", 1933.97D)

Code that looks up a value in the sorted list based on a key

Dim employeeKey As String = "Lewis"

Dim salesTotal As Decimal = salesList(employeeKey)

Code that converts the sorted list to a tab-delimited string

Dim salesTableString As String = ""

For Each employeeSalesEntry _

As KeyValuePair(Of String, Decimal) In salesList

salesTableString &= employeeSalesEntry.Key _

& vbTab & _

employeeSalesEntry.Value & vbCrLf

Next

MessageBox.Show(salesTableString, "Sorted List Totals")

Properties and methods of the Queue() class

PropertyDescription

CountGets the number of items in the queue.

MethodDescription

Enqueue(object)Adds the specified object to the end of the queue.

Dequeue()Gets the object at the front of the queue and removes it from the queue.

Clear()Removes all items from the queue.

Peek()Retrieves the next item in the queue without deleting it.

Code that uses a queue

Dim nameQueue As New Queue(Of String)

nameQueue.Enqueue("Boehm")

nameQueue.Enqueue("Murach")

nameQueue.Enqueue("Vasquez")

Dim nameQueueString As String = ""

Do While nameQueue.Count > 0

nameQueueString &= nameQueue.Dequeue & vbCrLf

Loop

MessageBox.Show(nameQueueString, "Queue")The message thats displayed

Properties and methods of the Stack() class

PropertyDescription

CountGets the number of items in the stack.

MethodDescription

Push(object)Adds the specified object to the top of the stack.

Pop()Gets the object at the top of the stack and removes it from the stack.

Clear()Removes all items from the stack.

Peek()Retrieves the next item in the stack without deleting it.

Code that uses a stack

Dim nameStack As New Stack(Of String)

nameStack.Push("Boehm")

nameStack.Push("Murach")

nameStack.Push("Vasquez")

Dim nameStackString As String = ""

Do While nameStack.Count > 0

nameStackString &= nameStack.Pop & vbCrLf

Loop

MessageBox.Show(nameStackString, "Stack")The message thats displayed

murach’s visual basic 2008, modified, c8© 2008, mike murach & associates, inc. slide 1

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