We are going to create a Plan abstract class and concrete classes that extends the Plan abstract class.When the parent classes choose the creation of objects to its sub-classes.When a class wants that its sub-classes specify the objects to be created.When a class doesn't know what sub-classes will be required to create.That means the code interacts solely with the resultant interface or abstract class, so that it will work with any classes that implement that interface or that extends that abstract class. It promotes the loose-coupling by eliminating the need to bind application-specific classes into the code.Factory Method Pattern allows the sub-classes to choose the type of objects to create.The Factory Method Pattern is also known as Virtual Constructor. In other words, subclasses are responsible to create the instance of the class. A Factory Pattern or Factory Method Pattern says that just define an interface or abstract class for creating an object but let the subclasses decide which class to instantiate.
