inner class and static method java

Question

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Why cant we have static method in an inner class?

I don't know why an inner class cannot have a static method. Why is it wrong?

class A1
{
    class B1
    {
         static void fun()
        {
            System.out.println("HIII");
        }
    }
    public static void main(String[] args)
    {
        A1 a = new A1();
        A1.B1 b = new a.B1();
        b.fun();
    }
}

If an outer class object can access a static method and a variable y not a inner class get the access? What are the problems.

Answer 1

The problem here is that your non-static inner class has a static method and you are trying to call it from static method of outer class.

Non-static inner class is "relevant" only in context of instance of outer class because it can access outer class' nont-static methods and to this of outer class (using A1.this).

Bottom line: if you want to do this mark inner class as static too:

static class B1
{
     static void fun()
    {
        System.out.println("HIII");
    }
}

Now you can call its static methods from outer class's static method.