Can static and abstract keyword used together in java?

Question

As I know that static and final combination can be used together but static and abstract or final and abstract combination is not allowed in java. But some where I have seen code like below

public class Enclosing {

    private static int x = 1;

    public static abstract class StaticNested {

        public abstract void run();
    }
  }

Can someone please explain the the concept and practical uses of this scenario.

Do you understand [what it means for a nested class to be static](https://stackoverflow.com/questions/70324/java-inner-class-and-static-nested-class)? Do you understand [what it means for a class to be abstract](https://stackoverflow.com/questions/1320745/abstract-class-in-java)? If you understand both those things then you'll understand the concept of an abstract static nested class. — Slaw, Mar 23 '20 at 05:15
Short answer: No. Longer answer: No, because it would not be useful. — Bohemian, Mar 23 '20 at 05:25
@Bohemian Static nested _classes_ certainly can be abstract and have the same valid uses as top-level abstract classes. That said, static _methods_ cannot be abstract, but the OP used a class as an example and not a method. — Slaw, Mar 23 '20 at 05:28

score 2 · Accepted Answer · edited Jun 20 '20 at 09:12

static and abstract can be used together for nested classes, eg

class A {
    static abstract class B {
        abstract void someMethod();
    }
}

B is a static nested class that requires concrete subclasses to implement someMethod().

but cannot be used together for methods, eg

static abstract void someMethod();  // compile error

Of course abstract and final can't be used together - such a combination would be nonsensical.

Uses of `static abstract class`

A suitable use of a static abstract class would be for node-like objects that only your class uses, for example a class the represent an entry in a map (eg java.util.Map.Entry which is an interface, but could have been a static abstract class), or a class for a node of a LinkedList, but one where the implementation is left to implementatioons of the enclosing class that themselves also use and provide implementations of the nested class by extending it too.

Can static and abstract keyword used together in java?

1 Answers1

Uses of static abstract class

Uses of `static abstract class`