Java Design Patterns Tutorial - Java Design Pattern - Abstract Factory Pattern

• « Previous
• Next »

Abstract Factory pattern is another creational pattern.

Abstract Factory patterns, also called as Factory of factories, have a factory which creates other factories.

When using Abstract Factory pattern, we first use super factory to create factory, then use the created factory to create objects.

Example

The following code shows how to use abstract factory pattern.

We are going to create shapes and Printers. For shapes, we would have circle, rectangle and square. For printers we will have paper Printer, Web Printer and screen Printer.

For shape we will create Shape interface, as follows

interface Shape {
   void draw();
}

Then we create concrete classes implementing the Shape interface.

class Rectangle implements Shape {

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

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

   @Override
   public void draw() {
      System.out.println("Inside Circle::draw() method.");
   }
}

After that we create an interface for Printers.

interface Printer{
   void print();
}

Then we create concrete classes implementing the Printer interface.

class PaperPrinter implements Printer{

   @Override
   public void print() {
      System.out.println("paper");
   }
}
class WebPrinter implements Printer{

   @Override
   public void print() {
      System.out.println("web");
   }
}
class ScreenPrinter implements Printer{

   @Override
   public void print() {
      System.out.println("screen");
   }
}

Finally we create an abstract class to get factories for Printer and Shape Objects.

abstract class AbstractFactory {
   abstract Printer getPrinter(String type);
   abstract Shape getShape(String shape) ;
}

Finally we create Factory classes extending AbstractFactory to generate object of concrete class based on given information.

class ShapeFactory extends AbstractFactory {
  
   @Override
   public Shape getShape(String shapeType){
      if(shapeType == null){
         return null;
      }    
      if(shapeType.equalsIgnoreCase("CIRCLE")){
         return new Circle();
      } else if(shapeType.equalsIgnoreCase("RECTANGLE")){
         return new Rectangle();
      } else if(shapeType.equalsIgnoreCase("SQUARE")){
         return new Square();
      }
      return null;
   }
   
   @Override
   Printer getPrinter(String type) {
      return null;
   }
}
class PrinterFactory extends AbstractFactory {
  
   @Override
   public Shape getShape(String shapeType){
      return null;
   }
   
   @Override
   Printer getPrinter(String type) {
   if(type == null){
      return null;
    }    
  if(type.equalsIgnoreCase("paper")){
      return new PaperPrinter();
  } else if(type.equalsIgnoreCase("web")){
      return new WebPrinter();
  } else if(type.equalsIgnoreCase("Screen")){
      return new ScreenPrinter();
  }
  return null;
 }
}

Create a Factory generator/producer class to get factories by passing an information such as Shape or Printer

class FactoryProducer {
   public static AbstractFactory getFactory(String choice){
      if(choice.equalsIgnoreCase("SHAPE")){
         return new ShapeFactory();
      } else if(choice.equalsIgnoreCase("Printer")){
         return new PrinterFactory();
      }
      return null;
   }
}

The following code shows how to use the abstract factory patterns.

public class Main {
   public static void main(String[] args) {

      //get shape factory
      AbstractFactory shapeFactory = FactoryProducer.getFactory("SHAPE");

      //get an object of Shape Circle
      Shape shape1 = shapeFactory.getShape("CIRCLE");

      //call draw method of Shape Circle
      shape1.draw();

      //get an object of Shape Rectangle
      Shape shape2 = shapeFactory.getShape("RECTANGLE");

      //call draw method of Shape Rectangle
      shape2.draw();
      
      //get an object of Shape Square 
      Shape shape3 = shapeFactory.getShape("SQUARE");

      //call draw method of Shape Square
      shape3.draw();

      //get printer factory
      AbstractFactory printerFactory = FactoryProducer.getFactory("printer");

    Printer printer1 = printerFactory.getPrinter("Paper");
    printer1.print();
    Printer printer2 = printerFactory.getPrinter("Web");
    printer2.print();
    Printer printer3 = printerFactory.getPrinter("Screen");
    printer3.print();
   }
}

The code above generates the following result.

• Next »
• « Previous