Before Java 8, there were many more differences between interfaces and abstract classes, but with the introduction of default, non-abstract, and static methods in interfaces, the difference has narrowed significantly.
See what still stands as the difference between these two types:
| Abstract Class | Interface | |
| Methods | Can have final methods but can not have default methods. | Supports default methods but can not have final methods declared. |
| Fields | It can have static, non-static, and final and non-final variables. It also supports private, protected, and public variables. |
Don’t support non-static and non-final variables.
Can have only public, static and final variables. |
| Constructors | Can have any number of constructors. | Can’t have constructors. |
| Member’s Accessibility | Support all types of members – private, protected, and public. | Don’t support protected members. (private – yes, after Java 9) |
| Inheritance | It can extend only one class but can implement multiple interfaces. | It can extend multiple interfaces but can not extend a class. |
