Tag: How to choose between interface and abstract class in Java

Use an abstract class if you have some functionality that you want it’s subclasses to have . For instance, if you have a set of functions that you want all of the base abstract class’s subclasses to have. Use an interface if you just want a general contract on behavior/functionality.

The main advantages of interface over abstract class is to overcome the occurrence of diamond problem and achieve multiple inheritance . In java there is no solution provided for diamond problem using classes. For this reason multiple inheritance is block using classes in java.

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. … Abstract classes can’t have default methods.

If an abstract class contains only abstract method declarations, it should be declared as an interface instead . Multiple interfaces can be implemented by classes anywhere in the class hierarchy, whether or not they are related to one another in any way.

The performance of an abstract class is fast . The performance of interface is slow because it requires time to search actual method in the corresponding class. It is used to implement the core identity of class.

4. 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.10 Haz 2021