Interfaces are the reference type in java that contains abstract methods. basically, interface declare the behaviors, and class implements that behavior Abstract Class are similar to regular classes except it cannot be initiated. it may or may not have an abstract method. one of the use-cases of the abstract class would be providing a base class that can be inherited. For Example. you want to create a class that will have some general method and some unique method. You should create an abstract class with a regular method and a unique method should be abstract so the sub-class can extend and implement its own implementation.