Design Patterns

                                                      Design pattern

1. Factory Design Pattern 

In Factory pattern, we create object without exposing the creation logic to the client and refer to newly created object using a common interface.

Step 1

Create an interface

IShape.cs

public interface IShape {
   void draw();
}

Step 2

Create concrete classes implementing the same interface.

Rectangle.cs
public class Rectangle : IShape {

   @Override
   public void draw() {
      Console.WriteLine("Inside Rectangle::draw() method.");
   }
}

Square.cs
public class Square : IShape {

   @Override
   public void draw() {
      Console.WriteLine("Inside Square::draw() method.");
   }
}

Circle.cs
public class Circle : IShape {

   @Override
   public void draw() {
      Console.WriteLine("Inside Circle::draw() method.");
   }
}

Step 3

Create a Factory to generate object of concrete class based on given information.

ShapeFactory.cs
public class ShapeFactory {
 
   //use getShape method to get object of type shape 
   public IShape 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;
   }
}

Step 4

Use the Factory to get object of concrete class by passing an information such as type.

FactoryPatternDemo.cs
public class FactoryPatternDemo {

   public static void main(String[] args) {
      ShapeFactory shapeFactory = new ShapeFactory();

      //get an object of Circle and call its draw method.
      Shape shape1 = shapeFactory.getShape("CIRCLE");

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

      //get an object of Rectangle and call its draw method.
      Shape shape2 = shapeFactory.getShape("RECTANGLE");

      //call draw method of Rectangle
      shape2.draw();

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

      //call draw method of circle
      shape3.draw();
   }
}

Step 5

Verify the output.
Inside Circle::draw() method.
Inside Rectangle::draw() method.
Inside Square::draw() method.