implementing static methods for interface

Question

suppose I have an interface:

public interface abcd{
    public int a();
    public void b();
    public void c();
    public String d(String h, String j);
}  

and I implement it in some class:

public class xyzw implements abcd{

}  

but I want the method d() to be static, but I can't do this:

public class xyzw implements abcd{
    public static void c(){
       //some code
    }
}

neither can I do this:

public interface abcd{
    public int a();
    public void b();
    public static void c();
    public String d(String h, String j);
}  

I wonder if there is something or some workaround or some language construct which allows me to make a method defined by an interface a static method?

Answer 1

You can define a static method in interface, but only with implementation.

public interface A {
    public static void b() {
        System.out.println("Hi");
    }
}

Overriding of static methods is not allowed in Java, because you call it on Class object, not on implementation object.

Answer 2

If you can implement a static method in an interface, but you cannot overwrite it, remember that a static method is referenced by the class itself and not by an instance of it.

To solve your problem maybe you could define an abstract class

Answer 3

No, its not possible and doesn't make any sense. An interface is meant to be implemented by subclasses you can only hava a non-abstract, implemented, static method in an interface. You could not statically call your interface method with

abcd.c()

when it has no implementation. Thats why static elements can not be overridden.

Answer 4

It's not possible to override static methods in java.

However, in the subclass, you can declare static method with the same name and "mask it as" the original method - which is as close as you can get.

interface a {
    public static int f() {
        return 0;
    }
}
interface b extends a {
    public static int f() {
        return 1;
    }
}
System.out.println(a.f());
>> 0

System.out.println(b.f());
>> 1