Advanced Topics - Static vs. Non-Static
Introduction
When the Modularization topic was covered, all the methods were declared as static. Yet, when the OOP topic was covered, all the class methods were not. Why the difference? This advanced topic will demonstrate the difference.
Sample Code
Static Class
namespace Static_vs_NonStatic_Demo
{
public class DistanceStatic
{
public static double KilometersToMiles(double kilometers)
{
double miles;
miles = kilometers * 0.621371192237334;
return miles;
}//end of KilometersToMiles
public static double MilesToKilometers(double miles)
{
double kilometers;
kilometers = miles * 1.609344;
return kilometers;
}//end of MilesToKilometers
}//eoc
}//eon
Non-Static Class
namespace Static_vs_NonStatic_Demo
{
public class DistanceNonStatic
{
public double KilometersToMiles(double kilometers)
{
double miles;
miles = kilometers * 0.621371192237334;
return miles;
}//end of KilometersToMiles
public double MilesToKilometers(double miles)
{
double kilometers;
kilometers = miles * 1.609344;
return kilometers;
}//end of MilesToKilometers
}//eoc
}//eon
Main Program
namespace Static_vs_NonStatic_Demo
{
class Program
{
static void Main(string[] args)
{
Setup();
int option,
type;
double miles,
kilometers;
do
{
DisplayTypeMenu();
type = GetSafeInt("Option: ");
if(type != 3)
{
DisplayOptionMenu();
option = GetSafeInt("Option: ");
if(type == 1)
{
//static method calls
if (option == 1)
{
//kms to miles
kilometers = GetSafeDouble("Enter kms: ");
miles = DistanceStatic.KilometersToMiles(kilometers);
Console.WriteLine("{0} kms = {1} miles", kilometers, miles);
}
else
{
//miles to kms
miles = GetSafeDouble("Enter miles: ");
kilometers = DistanceStatic.MilesToKilometers(miles);
Console.WriteLine("{0} miles = {1} kms", miles, kilometers);
}
}
else
{
//non-static method calls
DistanceNonStatic convert = new DistanceNonStatic();
if (option == 1)
{
//kms to miles
kilometers = GetSafeDouble("Enter kms: ");
miles = convert.KilometersToMiles(kilometers);
Console.WriteLine("{0} kms = {1} miles", kilometers, miles);
}
else
{
//miles to kms
miles = GetSafeDouble("Enter miles: ");
kilometers = convert.MilesToKilometers(miles);
Console.WriteLine("{0} miles = {1} kms", miles, kilometers);
}
}
}
} while (type != 3);
Console.ReadLine();
}//eom
static void Setup()
{
Console.Title = "Static vs. Non-static Demo";
Console.ForegroundColor = ConsoleColor.Black;
Console.BackgroundColor = ConsoleColor.White;
Console.Clear();
}//end of Setup
static void DisplayOptionMenu()
{
Console.WriteLine("\nSelect from one of the options below:");
Console.WriteLine("\t1. Kilometers to Miles");
Console.WriteLine("\t2. Miles to Kilometers");
}//end of DisplayOptionMenu
static void DisplayTypeMenu()
{
Console.WriteLine("\nSelect from one of the options below:");
Console.WriteLine("\t1. Static Methods");
Console.WriteLine("\t2. No-static Methods");
Console.WriteLine("\t3. Exit");
}//end of DisplayTypeMenu
static int GetSafeInt(string prompt)
{
int number = 1;
bool isValid = false;
do
{
try
{
Console.Write("{0,20}", prompt);
number = int.Parse(Console.ReadLine());
if (number >=1 && number <= 3)
{
isValid = true;
}
else
{
Console.WriteLine("ERROR: Invalid number ... try again");
}
}
catch (Exception)
{
Console.WriteLine("ERROR: Invalid number ... try again");
}
} while (!isValid);
return number;
}//end of GetSafeInt
static double GetSafeDouble(string prompt)
{
double number = 1;
bool isValid = false;
do
{
try
{
Console.Write("{0,20}", prompt);
number = double.Parse(Console.ReadLine());
if (number >= 0)
{
isValid = true;
}
else
{
Console.WriteLine("ERROR: Invalid number ... try again");
}
}
catch (Exception)
{
Console.WriteLine("ERROR: Invalid number ... try again");
}
} while (!isValid);
return number;
}//end of GetSafeDouble
}//eoc
}//eon
Output
What is the Difference?
The two outputs appear to be identical so what is the difference? Examining the first conversion you will see the following code for the static call:
And the following for the non-static call:
The difference is when the method is static you can access the method directly. If it is not declared as static you must create an instance (object) from the class before you can call the method.