If an abstract class can't be instantiated, why is the following possible?

Question

In the following code a Graphics object is passed into the following paintComponent method, which is then cast into a Graphics2D object. Isn't Graphics an abstract class so why is the following possible?

 public void paintComponent(Graphics comp) {
 Graphics2D comp2D = (Graphics2D) comp;
 Font font = new Font("Comic Sans", Font.BOLD, 15);
 comp2D.setFont(font);
 comp2D.drawString("Potrzebie!", 5, 50);
}

Answer 1

Just because a class can't be instantiated doesn't mean you can't get an instance of it.

In your example, all you are doing is casting it to a different class which is in the Graphics hierarchy.

Here's an example.

    public class AbstractDemo {

       public static void main(String[] args) {
          Concrete c = new Concrete();
          AClass a = (AClass) c;
          a.me();
       }

    }

    abstract class AClass {
       public void me() {
          System.out.println("Abstract parent");
       }
    }

    class Concrete extends AClass {

    }