Difference between Factory and Abstract Factory Design Pattern in Java

The Factory and Abstract Factory design patterns are both creational design patterns that help manage the creation of objects, but they have different use cases and structures. Here’s a detailed comparison of the two patterns:

Factory Method Pattern

1. Definition:

• The Factory Method pattern defines an interface for creating an object but lets subclasses alter the type of created objects. It is focused on a single product.

1. Structure:

• Involves a single factory class with a method that produces instances of a specific type (the product).
• Subclasses can override the factory method to create different types of products.

1. Use Case:

• When a class cannot anticipate the type of objects it needs to create.
• When a class wants its subclasses to specify the objects it creates.

1. Example:

• If you have an application that creates various types of notifications (Email, SMS), the Factory Method pattern would involve a single factory with methods to create each type of notification.

public interface Notification {
    void notifyUser();
}

public class EmailNotification implements Notification {
    @Override
    public void notifyUser() {
        System.out.println("Sending Email Notification");
    }
}

public class SMSNotification implements Notification {
    @Override
    public void notifyUser() {
        System.out.println("Sending SMS Notification");
    }
}

public abstract class NotificationFactory {
    public abstract Notification createNotification();
}

public class EmailNotificationFactory extends NotificationFactory {
    @Override
    public Notification createNotification() {
        return new EmailNotification();
    }
}

public class SMSNotificationFactory extends NotificationFactory {
    @Override
    public Notification createNotification() {
        return new SMSNotification();
    }
}

Abstract Factory Pattern

1. Definition:

• The Abstract Factory pattern provides an interface for creating families of related or dependent objects without specifying their concrete classes. It is focused on multiple products.

1. Structure:

• Involves multiple factory classes, each responsible for creating a family of related products.
• Each factory implements an interface or an abstract class to produce various products.

1. Use Case:

• When a system needs to be independent of how its objects are created, composed, and represented.
• When you need to create a set of related products that must work together.

1. Example:

• If you have an application that creates various types of UI components (Windows or Mac), the Abstract Factory pattern would involve multiple factories to create components like buttons, checkboxes, etc., for each OS.

public interface Button {
    void render();
}

public class WindowsButton implements Button {
    @Override
    public void render() {
        System.out.println("Rendering a Windows Button.");
    }
}

public class MacButton implements Button {
    @Override
    public void render() {
        System.out.println("Rendering a Mac Button.");
    }
}

public interface GUIFactory {
    Button createButton();
}

public class WindowsFactory implements GUIFactory {
    @Override
    public Button createButton() {
        return new WindowsButton();
    }
}

public class MacFactory implements GUIFactory {
    @Override
    public Button createButton() {
        return new MacButton();
    }
}

Summary of Differences

Conclusion

Both the Factory Method and Abstract Factory patterns help in managing object creation, but they serve different purposes and scenarios. The Factory Method is ideal when dealing with a single product type, while the Abstract Factory is suited for scenarios where a family of related objects is required. Understanding the differences can help you choose the right pattern based on your design needs.