Array & RandomSkill Area 306.3Materials Prepared by Dhimas Ruswanto, BMm

Lecture Overview

• Array• Random-Number

Generator

Array

• An array is a group of memory locations all containing data items of the same name and type.

• Array names follow the same conventions that apply to other identifiers.

Declaring Array

Dim myNumber(4) As Integer

name of array index type

• An array starts counting at zero, and the first position in your array will be zero

• An index must be either zero, a positive integer or an integer expression that yields a positive result

Allocating Array

Dim myNumbers(4) As Integer

myNumbers(0) = 1myNumbers(1) = 2myNumbers(2) = 3myNumbers(3) = 4myNumbers(4) = 5

value

Displaying Array

Dim myNumbers(4) As Integer

myNumbers(0) = 1myNumbers(1) = 2myNumbers(2) = 3myNumbers(3) = 4myNumbers(4) = 5

MsgBox("First Number is: " & myNumbers(0))MsgBox("Second Number is: " & myNumbers(1))MsgBox("Third Number is: " & myNumbers(2))MsgBox("Fourth Number is: " & myNumbers(3))MsgBox("Fifth Number is: " & myNumbers(4))

Example Array

Dim MyNumbers(4) As IntegerDim i As Integer MyNumbers(0) = 10MyNumbers(1) = 20MyNumbers(2) = 30MyNumbers(3) = 40MyNumbers(4) = 50 For i = 0 To 4  ListBox1.Items.Add(MyNumbers(i))Next

Example Array and Strings

Dim MyText(4) As StringDim i As Integer MyText(0) = "This"MyText(1) = "is"MyText(2) = "a"MyText(3) = "String"MyText(4) = "Array" For i = 0 To 4 ListBox1.Items.Add(MyText(i))Next

Assigning Values to ArrayDim numbers() As IntegerDim startAt As IntegerDim endAt As IntegerDim times As IntegerDim storeAnswer As IntegerDim i As Integer times = Val(TextBox1.Text)startAt = Val(TextBox2.Text)endAt = Val(TextBox3.Text) ReDim numbers(endAt) For i = startAt To endAt  storeAnswer = i * times numbers(i) = storeAnswer ListBox1.Items.Add(times & " times " & i & " = " & numbers(i))Next

Assigning values from TextBox

Non-Fixed size Arrayor

Dynamic Array

ReDim = reset an array then specify the new values

Random-Number GeneratorDim objRandom As Random = New Random()Dim intRandom As Integer =()

• The first statement declares objRandom as a reference of type

of Random and assigns it a Random object.• A reference is a variable to which you assign an object.

• Recall that keyword New creates a new structure value or a

new instance of an object in memory.

• The second statement declares Integer variable intRandom.

• It then assigns to it the value returned by calling Random ’s

Next method on objRandom using the dot operator

Method Call and Resulting Range

Method Call Resulting Range

objRandom.Next() 0 to one less than Int32.MaxValue

objRandom.Next(30) 0 to 29

10 + objRandom.Next(10) 10 to 19

objRandom.Next(10,20) 10 to 19

objRandom.Next(5,100) 5 to 99

objRandom.NextDouble() 0.0 to less than 1.0

8 * objRandom.NextDouble()

0.0 to less than 8.0

Examples RandomDim objRandom As Random = New Random()Dim intRandom As Integer = objRandom.Next(3) TextBox1.Text = intRandom

Dim objRandom As Random = New Random()Dim intRandom As Integer = objRandom.Next(3)Dim name As String() = New String() {"Hafiz", "Syazwan", "Irfan"} TextBox1.Text = name(intRandom)

Dim objRandom As Random = New Random()Dim intRandom As Integer = objRandom.Next(3)Dim number As Integer() = New Integer() {1, 5, 10} TextBox1.Text = number(intRandom)

Example 1:

Example 3:

Example 2:

--- continue to next slide ---