When would you have to make a class abstract?

An abstract class is a good choice if we are using the inheritance concept since it provides a common base class implementation to derived classes. An abstract class is also good if we want to declare non-public members. In an interface, all methods must be public.

Why would create an abstract class?

The short answer: An abstract class allows you to create functionality that subclasses can implement or override. An interface only allows you to define functionality, not implement it. And whereas a class can extend only one abstract class, it can take advantage of multiple interfaces.

Why would you create an abstract class if it can have no real instance?

No, you cannot create an instance of an abstract class because it does not have a complete implementation. The purpose of an abstract class is to function as a base for subclasses. It acts like a template, or an empty or partially empty structure, you should extend it and build on it before you can use it.

Why is abstraction needed?

Why is abstraction important? Abstraction allows us to create a general idea of what the problem is and how to solve it. The process instructs us to remove all specific detail, and any patterns that will not help us solve our problem. This helps us form our idea of the problem.

Why do we need abstract classes in Java?

Java Abstract class can implement interfaces without even providing the implementation of interface methods. Java Abstract class is used to provide common method implementation to all the subclasses or to provide default implementation. We can run abstract class in java like any other class if it has main() method.

Why would you create an abstract class if it can have no real instances?

Do we really need abstract class in Java?

3 Answers. An abstract class can be used as a type of template for other classes. The abstract class will hold common functionality for all classes that extend it.

Can we create abstract class without abstract method?

Yes we can have an abstract class without Abstract Methods as both are independent concepts. Declaring a class abstract means that it can not be instantiated on its own and can only be sub classed. Declaring a method abstract means that Method will be defined in the subclass.

What happens if we create object of abstract class?

No, we can’t create an object of an abstract class. The reference variable is used to refer to the objects of derived classes (subclasses of abstract class). An abstract class means hiding the implementation and showing the function definition to the user is known as Abstract class.

Can we create object of abstract class?

When and why to use abstract classes/methods?

An abstract class is a good choice if we are using the inheritance concept since it provides a common base class implementation to derived classes.

Should an abstract class have at least one abstract method?

When a class contains at least one abstract method, then the class must be declared as an abstract class. When a class is declared as an abstract class, then it is not possible to create an instance for that class. It can however be used as a parameter in a method. An abstract class can’t be a static class.

Why do we use abstract class?

Abstract classes are not instantiated directly. Abstract classes are useful when creating hierarchies of classes that model reality because they make it possible to specify an invariant level of functionality in some methods, but leave the implementation of other methods until a specific implementation of that class (a derived class) is needed.

When to use interface instead of abstract class?

If the functionality we are creating will be useful across a wide range of disparate objects,use an interface.