How can you use abstract classes instead of interfaces?

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.

1. Which is better to use abstract class or interface?
2. In which situation interface is better abstract class?
3. Why abstract classes are faster than interface?
4. Why would you use an abstract class?
5. What is purpose of abstract class?
6. Where did you use abstract class in your project?
7. Can we instantiate abstract class?
8. In which scenario we can use abstract class and interface?
9. When should you use abstract class vs interface or what is the difference between an abstract class and interface?
10. What is difference between abstract class and interface with real time example?
11. Why do we need interfaces in C#?
12. What are the similarities and differences between abstract classes and interfaces?
13. Can abstract class have non abstract methods?

Which is better to use abstract class or interface?

Abstract classes should be used primarily for objects that are closely related, whereas interfaces are best suited for providing a common functionality to unrelated classes. Interfaces are a good choice when we think that the API will not change for a while.

In which situation interface is better abstract class?

An interface is better than a abstract class when you want multiple classes to implement that interface and when you don't have to inherit default behavior. In order to provide WebServices or do JMock tests you dont need the actual implementation, you just need an interface definition.

Why abstract classes are faster than interface?

Method Resolution

The fourth difference between abstract class and interface in Java is that abstract classes are slightly faster than the interface because the interface involves a search before calling any overridden method in Java.

Why would you use an abstract class?

An abstract class is used if you want to provide a common, implemented functionality among all the implementations of the component. Abstract classes will allow you to partially implement your class, whereas interfaces would have no implementation for any members whatsoever.

What is purpose of abstract class?

An abstract class cannot be instantiated. The purpose of an abstract class is to provide a common definition of a base class that multiple derived classes can share.

Where did you use abstract class in your project?

When we have the requirement of a class that contains some common properties or methods with some common properties whose implementation is different for different classes, in that situation, it's better to use Abstract Class then Interface.

Can we instantiate abstract class?

Abstract classes cannot be instantiated, but they can be subclassed. When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract .

In which scenario we can use abstract class and interface?

If you want to implement or force some methods across classes must be for uniformity you can use an interface. So to increase reusability via inheritance use the abstract class as it is nothing but a base class and to force methods to use interfaces.

When should you use abstract class vs interface or what is the difference between an abstract class and interface?

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.

What is difference between abstract class and interface with real time example?

Abstract classes can have methods with implementation whereas interface provides absolute abstraction and can't have any method implementations. ... Abstract classes can have constructors but interfaces can't have constructors. Abstract class have all the features of a normal java class except that we can't instantiate it.

Why do we need interfaces in C#?

By using interfaces, you can, for example, include behavior from multiple sources in a class. That capability is important in C# because the language doesn't support multiple inheritance of classes. ... A class or struct can implement multiple interfaces, but a class can only inherit from a single class.

What are the similarities and differences between abstract classes and interfaces?

Both Interfaces and Abstract Classes can have methods and variables, but neither of them can be instantiated. All the variables declared within the interface are final. However, the variables declared in Abstract Classes can be non-final and can be modified by the user-defined classes.

Can abstract class have non abstract methods?

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.