Question: In which case, do we need abstract classes with no abstract methods?Answer: 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 superclass 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. Example: 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. |
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