Question

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Java: Static vs non static inner class

What is a static nested class?
What is the difference between static and non-static nested classes?

Answer 1

A static inner class is a class nested inside another class that has the static modifier. It’s pretty much identical to a top-level class, except it has access to the private members of the class it’s defined inside of.

class Outer {
    private static int x;
    static class Inner1 {
    }
    class Inner2 {
    }
}

Class Inner1 is a static inner class. Class Inner2 is an inner class that’s not static. The difference between the two is that instances of the non-static inner class are permanently attached to an instance of Outer — you can’t create an Inner2 without an Outer. You can create Inner1 object independently, though.

Code in Outer, Inner1 and Inner2 can all access x; no other code will be allowed to.