为什么Java中的本地类不能具有静态方法？

Question

In method main is class Counter that have method quantity that returns quantiny of numbers in given String.

 public static void main(String... args) {

    class Counter{
        static final String numbers="0123456789";
        int quantity(String main){
           int i=0;
            for (char c:main.toCharArray()){
                if (numbers.contains(Character.toString(c)))
                i++;
                }
         return i;
        }
    }

    String str="a0b3s2d6";
    Counter c=new Counter();
    System.out.println(c.quantity(str));
}

I think that creating instance of Counter is uselles, calling just Counter.quantity(str) will be easier than creating instance. So Why we can't have static methods in local classes?

Answer 1

Local classes can be only created when the parent class is initialized. Mentioning them static means that they should be created before the class initialization which wouldn't be possible.

For more details , see this

Answer 2

Static : static keyword to create fields and methods that belong to the class, rather than to an instance of the class.We make members and methods static so that it can be used elsewhere and called from anywhere by using class names but

If we will make members of inner class static still we wont be able to access it outside that class.

In this case an inner class is associated with an instance of its outer class, it cannot define any static methods itself. A static nested class cannot refer directly to instance variables or methods defined in its enclosing class, it can use them only through an object reference.

Answer 3

Because static methods could be called from anywhere of your code.

How would you call static method of the class Counter that you could not reach because it is in the local scope of some other class?

You're doing something wrong.

UPD

Why you trying to instantiate your static class?

Counter c=new Counter();

What goal are you actually trying to reach?

Answer 4

If you want call the method like Counter.quantity(str) ,You can define the class out the main method.

public static void main(String... args) {
    String str = "a0b3s2d6";
    System.out.println(Counter.quantity(str));
}

static class Counter {
    static final String numbers = "0123456789";

    static int quantity(String main) {
        int i = 0;
        for (char c : main.toCharArray()) {
            if (numbers.contains(Character.toString(c)))
                i++;
        }
        return i;
    }
}