1. CSCI 3327 Visual Basic Chapter 7: Arrays
UTPA – Fall 2011
Part of the slides is from Dr. John Abraham’s previous lecture slides. – Xiang Lian

2. Objectives In this chapter, you will:
Learn how arrays are used to store elements
Get familiar with the declaration, initialization, and reference to elements of the array
Know how to pass arrays to methods
Learn how to use For Each … Next statement to iterate through elements in the array

3. Arrays
An array is a group of variables (called elements) containing values that all have the same data type
For most languages, the number of elements are static and defined at declaration
In Visual Basic, arrays can be re-dimensioned at the execution time
Single dim, two dim and multiple dim

4. Example of an Array The first element is the zeroth element
C(0)
-45
C(1) 6
C(2)
C(3) 72
C(4) 34
C(5) 39
C(6) 98
C(7)
-1345
C(8)
939
C(9) 10
C(10) 40
C(11) 33
The first element is the zeroth element
The highest position number is array’s upper bound
Array C on RHS: 11
Access array elements
Use index (or subscript)
E.g., C(8)

5. Declaring an Array Declaration (different ways)
Dim Grades As Integer()
Grades = New Integer(0 to 11) {}
{} initializer list
Grades = New Integer(11) {}
Dim Grades() As Integer
Declare and initialize with initializer lists
Dim Grades() As Integer={90,80,88,90,70}
Local type inference
Dim Grades ={90,80,88,90,70}

6. Default Initialization
When you do not provide initializer list, elements are initialized to default values
Numeric primitive data type: 0
Boolean data type: False
String data type: Nothing

7. Referring to an Element
Name and position
Grades(6) = 85
First element is 0th index (subscript)
Index must be a nonnegative integer
Index may have a calculated value like Grades(i+4*2)
Know the difference between index and value stored there
Sum = Grades(1) + Grades(2) + Grades(3)

8. Array is a Class Class is in System.Array X = C.GetUpperBound(0)
-45
C(1) 6
C(2)
C(3) 72
C(4) 34
C(5) 39
C(6) 98
C(7)
-1345
C(8)
939
C(9) 10
C(10) 40
C(11) 33
Class is in System.Array
X = C.GetUpperBound(0)
Will give 11 (see the declaration)
X= C.GetLength(0)
Will give 12
X=C.Length

9. Example 7.2: InitializeArrays.vb
URL:
GetUpperBound(0)

10. Example 7.3: SumArray.vb URL: For i = 0 To values.GetUpperBound(0)
For i = 0 To values.GetUpperBound(0)
Total+= values(i)
Next

11. Example 7.4: StudentPoll.vb
URL:
IndexOutOf Range Exception
Try … statements
Catch ex As IndexOutOfRangeException
'handling exceptions
End Try

12. Example 7.5: DiceStatistics.vb
URL:
Summarize statistics of the dice
CType

13. Example 7.6: Flag Quiz URL: Properties of ComboBox
Properties of ComboBox
DropDownStyle: DropDownList (not editable)
MaxDropDownItems: the maximum number of items displayed at one time
CountriesComboBox.DataSource=countries 'array
CountriesComboBox.Selected Index = 0
Replace method of String: country.Replace(" ","")

14. Passing Arrays
Always as byVal (it is just a pointer to the 0th element)
Declaration
Dim scores(80) As Integer
Function standardDeviation(ByVal scores() As Integer, ByVal numscores As Integer) As Double
Call
stdDev = standardDeviation(scores, numScores)

15. Manipulating Array Using Loops
For i = 0 To scores.GetUpperBound(0)
Total += scores(i)
Next

16. For Each … Next Statement
For Each grade In gradeArray
Total += grade
Next
For Each grade As Integer In gradeArray