Factory Pattern

We’re going to create a Shape interface and concrete classes implementing the Shapeinterface. A factory class ShapeFactory is defined as a next step.

FactoryPatternDemo, our demo class will use ShapeFactory to get a Shape object. It will pass information (CIRCLE / RECTANGLE / SQUARE) to ShapeFactory to get the type of object it needs.

Factory Pattern UML Diagram

Step 1

Create an interface.


public interface Shape {
   void draw();

Step 2

Create concrete classes implementing the same interface.


public class Rectangle implements Shape {

   public void draw() {
      System.out.println("Inside Rectangle::draw() method.");


public class Square implements Shape {

   public void draw() {
      System.out.println("Inside Square::draw() method.");


public class Circle implements Shape {

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

Step 3

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


public class ShapeFactory {
   //use getShape method to get object of type shape 
   public Shape getShape(String shapeType){
      if(shapeType == null){
         return null;
         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.


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

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

      //call draw method of Rectangle

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

      //call draw method of circle

Step 5

Verify the output.

Inside Circle::draw() method.
Inside Rectangle::draw() method.
Inside Square::draw() method.