An interface is one of the types in java which doesn't have any implementation and it is just a group of method signature. This interface can't be created. The reason behind this fact is that these interfaces are just a collection of method signatures. Once we create an interface, we can't keep on adding new method in it. For example, we can't add a method in java.Aspect interface which will help us in modifying the class behavior from outside the class. As this goes against the object-oriented programming principle. In reality interfaces are nothing but java annotations extension. We should use interfaces to keep our code light.