Java factory mode

Java Design Mode - Factory Mode

Factory mode is a creation pattern because it provides a better way to create objects.

In factory mode, we create objects without exposing the creation logic to the client.

Example

In the following sections, we'll show you how to create objects using factory mode.

Objects created by factory mode will be shape objects, such as circles and rectangles.

First, we design an interface to represent Shape.

public interface Shape {
   void draw();
}

Then we create a specific class that implements the interface.

The following code is used for 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.");
   }
}

Circle.java

public class Circle implements Shape {

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

The core factory pattern is a Factory class. The following code shows how to create a Factory class for a Shape object.

The ShapeFactory class creates a Shape object based on the String value passed to the getShape() method. If the String value is CIRCLE, it creates a Circle object.

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

The following code has a main method, and it uses the Factory class to get class-specific objects by passing information such as types.

public class Main {

   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();
   }
}

The code above produces the following results.