What is Interface in Java?

Interfaces (defining, implementation, nesting, applying), variables in interfaces, extending interfaces, instance of operator.

Nested Interface:

    by declaring one interface within another interface, we can organize similar or related interfaces in a more readable and logical way so that you can make your code simpler to understand and modify.

    If you want to limit the interface scope and wants to prevent it from being accessed outside of that class.

instanceof Operator:

    If you want to check the type of an object, I mean to say this operator allows us to check if an object belongs to a particular interface, class, or subclass. It returns a Boolean value. if an object belongs to a particular class, subclass, or interface then it returns true otherwise false.