When is abstract class used java

To access the abstract class, it must be inherited from another class. Let's convert the Animal class we used in the Polymorphism chapter to an abstract class:. Remember from the Inheritance chapter that we use the extends keyword to inherit from a class. Try it Yourself ». Note: Abstraction can also be achieved with Interfaces , which you will learn more about in the next chapter. We just launched W3Schools videos. A method which is declared as abstract and does not have implementation is known as an abstract method.

In this example, Bike is an abstract class that contains only one abstract method run. Its implementation is provided by the Honda class. In this example, Shape is the abstract class, and its implementation is provided by the Rectangle and Circle classes. Mostly, we don't know about the implementation class which is hidden to the end user , and an object of the implementation class is provided by the factory method.

A factory method is a method that returns the instance of the class. We will learn about the factory method later. In this example, if you create the instance of Rectangle class, draw method of Rectangle class will be invoked. An abstract class can have a data member, abstract method, method body non-abstract method , constructor, and even main method.

The abstract class can also be used to provide some implementation of the interface. In such case, the end user may not be forced to override all the methods of the interface. JavaTpoint offers too many high quality services.

Mail us on [email protected] , to get more information about given services. Please mail your requirement at [email protected] Duration: 1 week to 2 week. Java Training Basics of Java. Abstract class Interface Abstract vs Interface. Thanks for visiting DZone today,. Edit Profile. Sign Out View Profile. Over 2 million developers have joined DZone.

When to Use Abstract Class and Interface. Learn when it would be more helpful to use an abstract class in Java rather than the interface. Like Believe me its too easy to import a class with same name but from different package with code auto-completion feature of modern IDEs. Though, its not mandatory not ensured by any compiler rule to have abstract method inside abstract class, but this is not advisable, because there is no point doing it.

If your class don't have any abstract behaviour behaviour which changes between different types then its good candidate of being a concrete class rather than abstract. There is only one case where I think abstract class without abstract method can be used is when you need a marker class instead of marker interface, but to be frank, I have yet to find a practical use case.

Though thinking a class as abstract at start can be good for discovering some level of abstraction. It's completely free and you just need a free Udemy account to join this course. Labels: core java , Java programming Tutorial , object oriented programming , programming. Rohan June 16, at AM. Unknown July 5, at AM. Unknown July 31, at AM. Mahesh November 1, at AM. Anonymous April 6, at AM. Tanish March 4, at AM. Anonymous June 18, at AM. Unknown December 3, at AM. Anonymous July 6, at AM.

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