Template method pattern

An abstract class is a class declared with an abstract keyword which is a collection of abstract and non-abstract methods while a concrete class is a class that allows creating an instance or an object using the new keyword. Thus, this is the main difference between abstract class and concrete class.

An abstract class can contain sealed methods but an abstract method or class cannot be declared as sealed . A subclass of an abstract class can only be instantiated if it implements all of the abstract methods of its superclass. Such classes are called concrete classes to differentiate them from abstract classes.

A concrete method means, the method has complete definition but it can be overridden in the inherited class . If we make this method “final” then it can not be overriden. Declaring a method or class “final” means its implementation is complete.

What Is a Concrete Class? A concrete class is a class that we can create an instance of, using the new keyword . In other words, it’s a full implementation of its blueprint. A concrete class is complete.