Java - No enclosing instance of type Foo is accessible

Question

I have the following code:

class Hello {
    class Thing {
        public int size;

        Thing() {
            size = 0;
        }
    }

    public stat         


        

Answer 1

Lets understand it with the following simple example. This happens because this is NON-STATIC INNER CLASS. You should need the instance of outer class.

 public class PQ {

    public static void main(String[] args) {

        // create dog object here
        Dog dog = new PQ().new Dog();
        //OR
        PQ pq = new PQ();
        Dog dog1 = pq.new Dog();
    }

    abstract class Animal {
        abstract void checkup();
    }

    class Dog extends Animal {
        @Override
        void checkup() {
            System.out.println("Dog checkup");

        }
    }

    class Cat extends Animal {
        @Override
        void checkup() {
            System.out.println("Cat Checkup");

        }
    }
}