sealed class PI
{
public static float number;
static PI()
{ number = 3.141592653F; }
static public float val()
{ return number; }
}
What's the difference between public static and static public? Can they be used in any order?
How would I use static public float val()?
Does it get executed as soon as the class is initialized?
There's no difference. You're free to specify them in either order.
However, I find that most developers tend to use:
public static
and NOT static public.
About the ordering of modifiers
They can be used in any order. It's just a stylistic choice which one you use. I always use visibility first, and most other code does too.
About the second question:
static public float val()
This is just a static function. You call it with PI.val(). You just don't need an instance of the class to call it, but call it on the class directly. A static function does not receive a this reference, can't be virtual, it's just like a function in a non OOP language, except that it's using the class as namespace.
Well, it is just like the name of a Person =) Calling Tom Mike or Mike Tom, no difference.
There is no difference. Their order is not important with respect to each other
To answer your second question, it should probably be written as
public static class Pi
{
private static float pi = 0;
public static float GetValue()
{
if (pi == 0)
pi = 3.141592653F; // Expensive pi calculation goes here.
return pi;
}
}
And call it thusly:
float myPi = Pi.GetValue();
The reason for writing such a class is to cache the value, saving time on subsequent calls to the method. If the way to get pi required a lot of time to perform the calculations, you would only want to do the calculations once.
With regards to the second question: The method is available without an instance of a class, it could be called thusly:
PI.val();
Because the class only has static members, the class should probably be a static class, and then it could never get initialized.
