Both Abstract classes and interfaces in Java follow the principle of writing code for interface rather than the implementation. This principle ensures that flexibility is added to the code to tackle dynamic requirements. Some of the pointers for deciding what to prefer over what are as follows:
Java lets to extend only one class and let’s implement multiple interfaces. If we extend one class then we cannot extend other classes. In such cases, it is better to implement the interfaces wherever possible and reserve the inheritance of classes to only important ones.
Interfaces are used for representing the behaviour of the class. Java lets to implement multiple interfaces which is why we can take the help of interfaces to help classes have multiple behaviours at the same time.
Abstract classes are slightly faster than interfaces. It can be used for time-critical applications.
In cases where there are common behaviours across the inheritance hierarchy, these can be coded at one place in abstract classes. Interfaces and abstract classes can also be used together to define a function in interface and functionality in abstract class.
