Why interface is used instead of abstract class?

Inhaltsverzeichnis:

1. Why interface is used instead of abstract class?
2. Can we override abstract method?
3. Can we inherit final method?
4. Can we declare constructors as final?
5. Can we have static class?
6. Can constructor declared as private?
7. Can a constructor call a static method in Java?
8. Can we make the abstract method Static in Java?
9. Why do we use static?

Why interface is used instead of 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.

Can we override abstract method?

An abstract method has no implementation. ... Subclasses of an abstract class must implement (override) all abstract methods of its abstract superclass. The non-abstract methods of the superclass are just inherited as they are. They can also be overridden, if needed.

Can we inherit final method?

No, we cannot override a final method in Java. The final modifier for finalizing the implementations of classes, methods, and variables. We can declare a method as final, once you declare a method final it cannot be overridden.

Can we declare constructors as final?

No, a constructor can't be made final. A final method cannot be overridden by any subclasses. ... But, in inheritance sub class inherits the members of a super class except constructors. In other words, constructors cannot be inherited in Java therefore, there is no need to write final before constructors.

Can we have static class?

We can declare a class static by using the static keyword. A class can be declared static only if it is a nested class. It does not require any reference of the outer class. ... To understand the concept of static class first we need to understand the concept of inner, outer, and nested class.

Can constructor declared as private?

Yes, we can declare a constructor as private. If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.

Can a constructor call a static method in Java?

This is the reason why constructor cannot be static – Because if we make them static they cannot be called from child class thus object of child class cannot be created. ... If you made constructor as static then the constructor will be called before object creation same like main method.

Can we make the abstract method Static in Java?

If you declare a method in a class abstract to use it, you must override this method in the subclass. But, overriding is not possible with static methods. Therefore, an abstract method cannot be static.

Why do we use static?

In Java, static keyword is mainly used for memory management. It can be used with variables, methods, blocks and nested classes. It is a keyword which is used to share the same variable or method of a given class. Basically, static is used for a constant variable or a method that is same for every instance of a class.