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The factory pattern is a creational design pattern that provides a way to create objects without specifying the exact class of the object being created. It uses factory methods to deal with object creation. The factory pattern defines a common interface for creating objects but allows subclasses to determine which class to instantiate. The document describes implementing a factory pattern to create different shape objects like circle, rectangle and square by passing a string to the factory class to determine which object to return. It defines a shape interface and concrete classes, a factory class that returns the appropriate shape object based on the string, and a demo class that uses the factory to get shape objects.
![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.");
}
}
Step 3
Create a Factory to generate object of concrete class based on given information.
ShapeFactory.java
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;
}
}
Step 4
Use the Factory to get object of concrete class by passing an information such as type.
FactoryPatternDemo.java
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");](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
