Sage-Tips

Why do we use interface reference in Java?

Why do we use interface? It is used to achieve total abstraction. Since java does not support multiple inheritance in case of class, but by using interface it can achieve multiple inheritance . The reason is, abstract classes may contain non-final variables, whereas variables in interface are final, public and static.

What is the use of an interface reference?

An interface reference variable only knows that methods which are declared by its interface declaration. It does not allow accessing any other variables or methods that might be supported by the objects. This concept is similar when you use a parent class reference to access a child class object.

What is interface reference variable in Java?

A reference variable declared using an interface name as its type can only reference instances of classes that implement that interface. For example, Java provides an interface called Runnable. Java also provides a class called Thread that implements Runnable.

Can we use interface reference in Java?

Yes, you can. If you implement an interface and provide body to its methods from a class. You can hold object of the that class using the reference variable of the interface i.e. cast an object reference to an interface reference.

Can one interface extend another interface?

An interface can extend another interface in the same way that a class can extend another class. The extends keyword is used to extend an interface, and the child interface inherits the methods of the parent interface.

How is interface implemented in Java?

An interface is declared by using the interface keyword. It provides total abstraction; means all the methods in an interface are declared with the empty body, and all the fields are public, static and final by default. A class that implements an interface must implement all the methods declared in the interface.

Can an interface be used as a data type?

When you define a new interface, you are defining a new reference data type. You can use interface names anywhere you can use any other data type name. When they implement Relatable , they can be of both their own class (or superclass) type and a Relatable type. …

CAN interface have final methods?

14 Answers. A final method can’t be overridden. All methods are instance methods. Since the only goal of an interface is to have classes implementing them, and since methods in interfaces can’t have any implementation, making them final would make no sense: they would have no implementation, and could not be overridden …

Can an interface be abstract?

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). All constant values defined in an interface are implicitly public , static , and final .

Why interface is useful?

Interfaces are useful for the following: Capturing similarities among unrelated classes without artificially forcing a class relationship. Declaring methods that one or more classes are expected to implement. Revealing an object’s programming interface without revealing its class.

What is the use of reference variable in Java?

1. Reference variable is used to point object/values. 2. Classes, interfaces, arrays, enumerations, and, annotations are reference types in Java. Reference variables hold the… 3. Reference variable can also store null value. By default, if no object is passed to a reference variable then it

What happens when you define an interface in Java?

When you define a new interface, you are defining a new reference data type. You can use interface names anywhere you can use any other data type name. If you define a reference variable whose type is an interface, any object you assign to it must be an instance of a class that implements the interface.

Where can I use interface names in Java?

You can use interface names anywhere you can use any other data type name. If you define a reference variable whose type is an interface, any object you assign to it must be an instance of a class that implements the interface.

What is the default variable type in an interface in Java?

In an interface, variables are static and final by default. All variables in an interface in java should have only public access modifier. here is a string variable “shapes” declared in the interface.