14A. Java Basics for Selenium - Java Interfaces - Key Points

1) We can’t instantiate an interface in java. That means we cannot create the object of an interface
2) Interface provides full abstraction as none of its methods have body. On the other hand abstract class provides partial abstraction as it can have abstract and concrete(methods with body) methods both.
3) implements keyword is used by classes to implement an interface.
4) While providing implementation in class of any method of an interface, it needs to be mentioned as public.
5) Class that implements any interface must implement all the methods of that interface, else the class should be declared abstract.
6) Interface cannot be declared as private, protected or transient.
7) All the interface methods are by default abstract and public.
8) Variables declared in interface are public, static and final by default.
9) Interface variables must be initialized at the time of declaration otherwise compiler will throw an error.
10) Inside any implementation class, you cannot change the variables declared in interface because by default, they are public, static and final.
11) An interface can extend any interface but cannot implement it. Class implements interface and interface extends interface.
12) A class can implement any number of interfaces.
13) If there are two or more same methods in two interfaces and a class implements both interfaces, implementation of the method once is enough.
14) A class cannot implement two interfaces that have methods with same name but different return type.
15) Variable names conflicts can be resolved by interface name.