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Visual Basic Compared to Java

Variable Usage


Variables are the short-term memory of computer programs. This is how your program remembers information while it is running.

Figure 1: Variable Usage
Java Visual Basic 

int i;// ints can store integer numbers
double d;// doubles can have decimal places
String s;// strings can hold characters

i = 10;
d = 3.14;
s = "Java";



Dim d As Double ' A double can hold decimal places
Dim i As Integer ' An integer can hold integers
Dim s As String ' A string can hold characters

d = 3.14
i = 10
s = "Visual Basic"

If Statements


Nearly every programming language has a way to make decisions. If statements are the usual means.

Operators Used with IF Statements
Name VB Java
Equal = ==
Not Equal <> !=
Greater Than > >
Less Than < <
Greater Than or Equal >= >=
Less Than or Equal < <


Figure 2: Simple If Statements
Java Visual Basic 

int a,b;

a=1;
b=2;

if(a==b)
{
	System.out.println("A and B are equal");
}
else
{
	System.out.println("A and B are not equal");
}


Dim a as integer
Dim b as integer

a=1
b=2

if a=b then
	MsgBox "A and B are equal"
else
	MsgBox "A and B are not equal"
end if

Compound If Statements


Compound if statements make decisions based on several things. This is done by using Boolean operators such as AND and OR.



Figure 3: Compound Simple If Statements
Java Visual Basic 

int a,b;

a=1;
b=2;

if( (a==b) || (a==2) )
{
	System.out.println("A and B are equal, or a equals 2");
}
else
{
	System.out.println("A and B are not equal or a is not 2");
}

if( (a==b) && (a==2) )
{
	System.out.println("A and B are equal, and a equals 2");
}
else
{
	System.out.println("A and B are not 2");
}


Dim a As Integer
Dim b As Integer

a = 1
b = 2

If (a = b) Or (a = 2) Then
    MsgBox "A and B are equal, or a equals 2"
Else
    MsgBox "A and B are not equal or a is not 2"
End If

If (a = b) And (a = 2) Then
    MsgBox "A and B are equal, and a equals 2"
Else
    MsgBox "A and B are not 2"
End If

While Loops

The ability to execute a section of code over and over is very important to a programming language. This is called a loop. Java has three types of loops: the while, do/while and for.



Figure 4: While Loops
Java Visual Basic 

int a;

a=1;

while( a<=10 )
{
	System.out.println("Counting: " + a + "..." );
	a = a + 1;// could also use the shorthand a++;
}



Dim a As Integer


a = 1

While (a <= 10)
    MsgBox "Counting: " & a & "..."
    a = a + 1 ' could also use the shorthand a++;
Wend

Do/While Loops


A do while loop is very much like a while loop, except that the decision to execute is made at the end of the loop. This means that a do/while loop must execute at least once.


Figure 5: Do/While Loops
Java Visual Basic 

int a;

a=1;

do
{
	System.out.println("Counting: " + a + "..." );
	a = a + 1;// could also use the shorthand a++;
} while( a<=10 );




a = 1

Do
    MsgBox "Counting: " & a & "..."
    a = a + 1 ' could also use the shorthand a++;
Loop While (a <= 10)

For Loops


A for loop is similar to a while loop. Except that much more is built into the loop command.


Figure 6: For Loops
Java Visual Basic 

int a;

// count from 1 to 10

for(a=1;a<=10;a++)
{
	System.out.println("Counting: " + a + "..." );
}

// count from 10 to 1

for(a=10;a>=1;a--)
{
	System.out.println("Counting: " + a + "..." );
}

// count from 2 to 10 by twos

for(a=2;a<=10;a+=2)
{
	System.out.println("Counting: " + a + "..." );
}




a = 1

Dim a As Integer

' count from 1 to 10

For a = 1 To 10
    MsgBox "Counting:" & a & "..."
Next a

' count from 10 to 1

For a = 10 To 1 Step -1
    MsgBox "Counting:" & a & "..."
Next a

' count from 2 to 10 by twos

For a = 2 To 10 Step 2
    MsgBox "Counting:" & a & "..."
Next a

Methods:Functions and Subs


Functions and subs allow you to create a block of code that can be executed from many different locations. Java makes no distinction between functions and subs. They are all called methods.


Figure 7: Functions and Subs
Java Visual Basic 

class HelloWorld
{
	public static void ExampleSub()
	{
		System.out.println("Calling the sub");
	}

	public static int ExampleFunction()
	{
		System.out.println("Calling the function");
		return 5;
	}

	public static int AddIt(int x,int y)
	{
		int result;

		System.out.println("Calling AddIt");
		result = x + y;

		return result;
	}
	public static void main(String args[])
	{
		ExampleSub();
		ExampleFunction();
		int t = AddIt(4,3);
		System.out.println("Output: " + t);
	}
}



Private Sub Form_Load()

Sub ExampleSub()
    MsgBox "Calling the sub"
End Sub

Sub ExampleFunction()
    MsgBox "Calling the function"
End Sub

Function AddIt(x As Integer, y As Integer) As Integer
    Dim result As Integer

    MsgBox "Calling AddIt"
    result = x + y
    AddIt = result
End Function

Sub main()
    ExampleSub
    ExampleFunction
    Dim t As Integer
    t = AddIt(4, 3)
    MsgBox "Output: " & t
End Sub