It is abstracted because they want to force you to extend it with your own functionality. Add a comment. Active Oldest Votes. Why should I declare a class as an abstract class? Community Bot 1 1 1 silver badge. Andrew Andrew 3 3 silver badges 8 8 bronze badges.
Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. The interface is similar to an abstract class as it is the grouping of abstract methods. When a class implements the interface, all the abstract methods within the interface are inherited.
The interface might also contain default methods, constants, and static methods. The method bodies of only the default and the static methods are present. While in the case of an interface only those behaviours of an object are present, those are implemented by the class.
A class has to define all the methods of the interface that it implements. Only for an abstract class, the methods are not required to be defined by the class. An interface is similar to a Java abstract class in the following ways:. An interface is different from a Java abstract class in the following ways:.
Total abstraction is provided through the use of an interface. By default, all the methods within an interface are abstract and public. This means there is nobody of the methods in an interface and all the fields are static, public, and final. More than one interface can be implemented by a class. The keyword is used in the class declaration. An example of a code showing the implementation of an interface in Java is shown below.
Generics: Inheriting from an abstract class that implements an interface Ask Question. Asked 9 years, 9 months ago. Active 9 years, 9 months ago. Viewed 63k times. Matt Matt 4, 5 5 gold badges 19 19 silver badges 26 26 bronze badges.
Add a comment. Active Oldest Votes. Alex Alex This is my most favorite answer in stackoverflow — silentsudo. And, we can access the constructor of an abstract class from the subclass using the super keyword. Here, we have used the super inside the constructor of Dog to access the constructor of the Animal. Note that the super should always be the first statement of the subclass constructor.
Visit Java super keyword to learn more. Abstraction is an important concept of object-oriented programming that allows us to hide unnecessary details and only show the needed information. This allows us to manage complexity by omitting or hiding details with a simpler, higher-level idea. A practical example of abstraction can be motorbike brakes. We know what brake does. When we apply the brake, the motorbike will stop. However, the working of the brake is kept hidden from us.
The major advantage of hiding the working of the brake is that now the manufacturer can implement brake differently for different motorbikes, however, what brake does will be the same. In the above example, we have created an abstract super class MotorBike. The superclass MotorBike has an abstract method brake. The brake method cannot be implemented inside MotorBike. It is because every bike has different implementation of brakes.
So, all the subclasses of MotorBike would have different implementation of brake. Here, MountainBike makes its own implementation of brake and SportsBike makes its own implementation of brake. Note : We can also use interfaces to achieve abstraction in Java. To learn more, visit Java Interface.
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