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Is It Possible To Define All The Methods In An Abstract Class?

  • It is possible create an abstract class with all concrete methods. But this class can’t be instantiated. Since it is an abstract class. 
  •   We may have situations where we don’t want to instantiate a class which is the base class for all the classes in the system or application.This base class may have lot of methods used for different modules in the application and we do not want to instantiate the object of the base class and want to use only the reference of the class.
  •  An abstract class without any abstract methods should be a rare thing and you should always question your application design if this case arises. Normally you should refactor to use a concrete super class in this scenario.
  •  One specific case where abstract class may justifiably have no abstract methods is where it partially implements an interface, with the intention that its subclasses must complete the interface.
  •        To take a slightly contrived motoring analogy, a Chassis class may partially implement a Vehicle interface and provide a set of core methods from which a range of concrete Vehicle types are extended. Chassis is not a viable implementation of a Vehicle in its own right, so a concrete Car subclass would have to implement interface methods for functional wheels, engine and bodywork.
       A class can be declared abstract even if it does not actually have any abstract methods. Declaring such a class abstract indicates that the implementation is somehow incomplete and is meant to serve as a superclass for one or more subclasses that will complete the implementation. Such a class cannot be instantiated. 

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