公共静态与静态公共-有区别吗？

Question

sealed class PI
{
  public static float number;
  static PI()
  { number = 3.141592653F; }
  static public float val()
  { return number; }
}

1. What's the difference between public static and static public? Can they be used in any order?

2. How would I use static public float val() ?

   Does it get executed as soon as the class is initialized?

Answer 1

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.

Answer 2

好吧，这就像一个人的名字=）叫Tom Mike或Mike Tom，没什么区别。

Answer 3

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.

Answer 4

There is no difference. Their order is not important with respect to each other

Answer 5

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.

Answer 6

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.