Question

I just started learning java when i came across interface, I saw the following code:

interface Callback {
   void callback(int param);
}

---

class Client implements Callback {
   public void callback(int p) {
   }
}

why is that an implemented interface method be declared as public?

Answer 1

The default modifier for an interface method is public abstract

The default modifier for a class method is package-local. These are not the same, and you can’t override a public method with a package local one. You can override an abstract method with a non-abstract one.

You have to make your class method public, even though you don’t have to put this in the interface.