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CAN interface have empty body?
To declare an interface, use interface keyword. It is used to provide total abstraction. 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.
Can an interface have methods with bodies?
The interface body can contain abstract methods, default methods, and static methods. An abstract method within an interface is followed by a semicolon, but no braces (an abstract method does not contain an implementation).
Which interface has only one method override?
An interface with exactly one abstract method is known as Functional Interface.
CAN interface have no method in it?
Yes, you can write an interface without any methods. These are known as marking interfaces or, tagging interfaces. A marker interface i.e. it does not contain any methods or fields by implementing these interfaces a class will exhibit a special behavior with respect to the interface implemented.
Why are constructors not part of the interface?
An Interface in Java doesn’t have a constructor because all data members in interfaces are public static final by default, they are constants (assign the values at the time of declaration). There are no data members in an interface to initialize them through the constructor.
Can a method in an interface have a body?
In the Java 7 Language Specification §9.4, it explicitly states: It is a compile-time error if a method declared in an interface is declared static, because static methods cannot be abstract. So in Java 7, static methods in interfaces cannot exist.
Can a static method be defined in an interface?
In addition to default methods, you can define static methods in interfaces. (A static method is a method that is associated with the class in which it is defined rather than with any object. Every instance of the class shares its static methods.)
Can a static method have a body in Java 7?
So in Java 7, static methods in interfaces cannot exist. A static method also has a block body, which provides the implementation of the method. So it explicitly states that in Java 8, they can exist.