Nesting Classes in an Interface Definition : Interface « Class Definition « Java Tutorial

1. Java Tutorial
2. Class Definition
3. Interface

An inner class to an interface will be static and public by default.

interface Port {
  // Methods & Constants declared in the interface...

  class Info {
    // Definition of the class...
  }
}

public class MainClass {
  public static void main(String[] a) {
    Port.Info info = new Port.Info();
  }
}