Abstract Factory Design Pattern

Abstract Factory patterns work around a super-factory which creates other factories.

This factory is also called as factory of factories. This type of design pattern comes under creational pattern

In Abstract Factory pattern an interface is responsible  for creating a factory of related objects without explicitly specifying their classes.

Each generated factory can give the objects as per the Factory pattern.

 

Below is the diagram and with code as example:

 

 

 

Step1. Create Shape Interface as shown in the above image with method draw.

Shape.java

public interface Shape {
   void draw();
}

Step 2. Create Concrete Classes implementing the same interface.

RoundedRectangle.java

public class RoundedRectangle implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside RoundedRectangle::draw() method.");
   }
}

RoundedSquare.java

public class RoundedSquare implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside RoundedSquare::draw() method.");
   }
}

Rectangle.java

public class Rectangle implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside Rectangle::draw() method.");
   }
}

Square.java

public class Square implements Shape {
   @Override
   public void draw() {
      System.out.println("Inside Square::draw() method.");
   }
}

Step3.

Create an Abstract class to get factories for Normal and Rounded Shape Objects.

public abstract class AbstractFactory {
   abstract Shape getShape(String shapeType) ;
}

Step 4

Create Factory classes extending AbstractFactory to generate object of concrete class based on given information.

ShapeFactory.java

public class ShapeFactory extends AbstractFactory {
   @Override
   public Shape getShape(String shapeType){    
      if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new Rectangle();         
      }else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new Square();
      }     
      return null;
   }
}

RoundedShapeFactory.java

public class RoundedShapeFactory extends AbstractFactory {
   @Override
   public Shape getShape(String shapeType){    
      if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new RoundedRectangle();         
      }else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new RoundedSquare();
      }     
      return null;
   }
}

Step 5.

Create a Factory generator/producer class to get factories by passing an information 

FactoryProducer.java

public class FactoryProducer {
   public static AbstractFactory getFactory(boolean rounded){   
      if(rounded){
         return new RoundedShapeFactory();         
      }else{
         return new ShapeFactory();
      }
   }
}

Step 6.

Use the FactoryProducer to get AbstractFactory in order to get factories of concrete classes by passing an information such as type.

AbstractFactoryPatternDemo.java

 

public class AbstractFactoryPatternDemo {
   public static void main(String[] args) {
      //get rounded shape factory
      AbstractFactory shapeFactory = FactoryProducer.getFactory(false);
      //get an object of Shape Rounded Rectangle
      Shape shape1 = shapeFactory.getShape("RECTANGLE");
      //call draw method of Shape Rectangle
      shape1.draw();
      //get an object of Shape Rounded Square 
      Shape shape2 = shapeFactory.getShape("SQUARE");
      //call draw method of Shape Square
      shape2.draw();
      //get rounded shape factory
      AbstractFactory shapeFactory1 = FactoryProducer.getFactory(true);
      //get an object of Shape Rectangle
      Shape shape3 = shapeFactory1.getShape("RECTANGLE");
      //call draw method of Shape Rectangle
      shape3.draw();
      //get an object of Shape Square 
      Shape shape4 = shapeFactory1.getShape("SQUARE");
      //call draw method of Shape Square
      shape4.draw();
      
   }
}