Abstract class using Java in NetBeans

abstract class Base {
    Base(){
        System.out.println("Base Constructor Called");
    }
    abstract void fun();
}
class Derived extends Base {
    Derived(){
        System.out.println("Derived Constructor Called");
    }
    void fun(){
        System.out.println("Derived fun() called");
    }
}
public class p29_abstractclass {
    public static void main(String args[]){
        Derived d = new Derived();
    } 
}