Can an anonymous inner class implement an interface?

--

Yes. An anonymous inner class can implement interface or extends class. Anonymous inner interfaces are always implicitly static.

Here is how to create an instance of inner class and inner interface:

• Anonymous Inner Class
  

  class Outer{
    abstract class InnerClass {
      abstract void doSomething();
    }
  }
  
  public class Program {
    public Program() {
      super();
    }
  
    public static void main(String[] args) {
      Outer.InnerClass obj = new Outer().new InnerClass(){
       public void doSomething(){
         System.out.println("InnerClass.");
       }
      };
      obj.doSomething();
    }
  
  }

• Anonymous Inner Interface:
  

  class Outer{
    interface InnerInterface {
      void doSomething();
    }
  }
  
  public class Program {
    public Program() {
      super();
    }
  
    public static void main(String[] args) {
      Outer.InnerInterface obj = new Outer.InnerInterface() {
         public void doSomething(){
            System.out.println("InnerInterface.");
         }
      };
      obj.doSomething();
    }
  
  }