What class must do when they implement an interface?

What class must do when they implement an interface?

Interfaces cannot be instantiated, but rather are implemented. A class that implements an interface must implement all of the non-default methods described in the interface, or be an abstract class.

Does class have to implement all interface methods?

Yes, it is mandatory to implement all the methods in a class that implements an interface until and unless that class is declared as an abstract class. Declare the class as an abstract class, as a result, forces you to subclass the class (and implement the missing methods) before you can create any objects.

When you implement an interface method it must be declared as public?

Interface methods are implicitly public in C# because an interface is a contract meant to be used by other classes. In addition, you must declare these methods to be public, and not static, when you implement the interface.

What does it mean for a class to implement an interface?

A class implements an interface, thereby inheriting the abstract methods of the interface. Along with abstract methods, an interface may also contain constants, default methods, static methods, and nested types. Method bodies exist only for default methods and static methods. An interface is written in a file with a .

Do you have to override interface methods?

The default methods are introduced in an interface since Java8. Unlike other abstract methods these are the methods can have a default implementation. If you have default method in an interface, it is not mandatory to override (provide body) it in the classes that are already implementing this interface.

Why is an interface method implemented in a class public?

Interfaces serve as a contract to code that uses your object saying you can always call any method defined in the interface on my object. If the implementing method were private, that would not longer be true. If you want to hide your implementation from, say Intellisense, then you can simply implement the method explicitly as @Bryan mentions.

Why is it not allowed to declare a public interface in Java?

Even you do not state a method as a public in interface it is public. But in your class, you have declared this method as package private. It is not allowed, because it reduces the visibility of the implemented method.

How are methods declared in an interface in Java?

That means all the methods in an interface are declared with an empty body and are public and all fields are public, static and final by default. A class that implements an interface must implement all the methods declared in the interface. To implement interface use implements keyword. Why do we use interface ?

Can a class extend another interface in Java?

An interface can extends another interface or interfaces (more than one interface) . A class that implements interface must implements all the methods in interface. All the methods are public and abstract. And all the fields are public, static, and final.