Interface and Abstract Class After Java 8

With the introduction of concrete methods (default and static methods) to interfaces from Java 8, the gap between interface and abstract class has been reduced significantly. Now both can have concrete methods as well as abstract methods. But, still there exist some minute differences between them. In this article, we will try to list down the differences between interface Vs abstract class after Java 8.

Differences Between Interface And Abstract Class After Java 8 :

1. Fields

   Interface fields are public, static and final by default. Interfaces still don’t support non-static and non-final variables. Interfaces can only have public, static and final variables. On the other hand, abstract class can have static as well as non-static and final as well as non-final variables. They also support private and protected variables along with public variables.

2. Methods

   After Java 8, an interface can have default and static methods along with abstract methods. Interfaces don’t support final methods. But, abstract classes support final as well as non-final methods and static as well as non-static methods along with abstract methods.

   Also note that, only interfaces can have default methods. Abstract classes can’t have default methods.

3. Constructors

   Interfaces can’t have constructors. Abstract classes can have any number of constructors.

4. Member’s Accessibility

   All members of interfaces are public by default. Interfaces don’t support private and protected members. But, abstract classes support all type of members – private, protected and public members.

5. Multiple Inheritance

   A class can extend only one abstract class, but can implement multiple interfaces. Thus, a class can inherit multiple properties from multiple sources only through interfaces, not through abstract classes.