Factory Pattern

Definition -
   
    When you can abstract the functionalities and use that object to call other classes which implement the

Scenario -

    Let us take an example of the production line itself, where the client places an order for a vehicle and depending on the order a hatchback or a sedan car is created.
In this case -
1. A abstract class called carmanufacture which have an execute funtion to process the request of the client. 

package SimpleFactoryPattern;

public class hatchback extends carmanufacture{

    @Override
    public void manufacture() {
        
        System.out.println("Manufacturing hatchback");
        
    }

}

2. There are two sub classes called hatchback and sedan which will extend the abstract class.

hatchback.java

package SimpleFactoryPattern;

public class hatchback extends carmanufacture{

    @Override
    public void manufacture() {
        
        System.out.println("Manufacturing hatchback");
        
    }

}

sedan.java    

package SimpleFactoryPattern;

public class sedan extends carmanufacture {

    @Override
    public void manufacture() {
        
        System.out.println("Manufacturing sedan");
        
    }
    
    

}

3. To see the pattern in action use the following code - 

package SimpleFactoryPattern;

public class factorydemo {
    
    public static void main(String args[]) {
        
        carmanufacture car=null;
        
        String order = "Hatchback";
        
        if(order.equalsIgnoreCase("Hatchback")) {
            car = new hatchback();
            
        }
        
        else if(order.equalsIgnoreCase("Sedan")) {
            car=new sedan();
        }
        
        car.manufacture();
        
    }

}

Place to use -
1) When you want the client to decide on the sub class at run time.
2) When you can abstract a class and there is not too much deviation in the way the different sub classes work.

Place not to use -
1) Can easily over complicate design.
2) When there are too many changes and each change introduces few attributes / functionalities not used by others then it might result in change.