doubts on questions #5 self-test Chapter 10

[John Lerry]

I have a doubt about the Factory pattern and particularly on the question #5 in the self test.

First I would like to understand if I understand the operation of the Factory pattern.
The main problem, that the use of the pattern tries to solve, is related to the change we want to do to a class to add functionality, in this case a change would also involve changing the main class.
To solve the problem the main class must only interact with an interface or an abstract class so that it does not interact with the class that takes care of the implementation.
This is an example taken from the book (K&B7):

public abstract class Factory {
         public abstract BookDao createDao();	
}
public class FactoryImpl extends Factory {      // class that takes care of the implementation
         public BookDao createDao() {
      	             return new InMemoryBookDao();
         }
}
public interface BookDao {
         // do stuff
}
public class Student {
         public static void main(String[] args) {
		    Factory factory = new FactoryImpl();   // the class interact with Factory
		    BookDao dao = factory.createDao();   // the class interact with BookDao
		    //
	    }
}		

Now we come to the question, I can not see the use of the Factory pattern in this code:

class A {}

abstract class G {
     A m() { return n(); }
     abstract A n();
}

Do you help me to understand?

[John Lerry]

nobody answers me?
sorry if I put this post but I'm afraid that this thread is not read.

[Paul Anilprem]

John Lerry wrote:
Now we come to the question, I can not see the use of the Factory pattern in this code:

class A {}

abstract class G {
     A m() { return n(); }
     abstract A n();
}

Do you help me to understand?

One would have to stretch the imagination quite a bit to consider the above code as a usage of factory pattern.

[John Lerry]

if the considerations made above on the Factory Pattern is correct I do not see absolutely the application of this pattern in that code.

the solution of the book says this:

Class A is the object we are creating using the factory method. Class G is the abstract superclass for the factory. Not shown is a class implementing class G that actually creates the object.