Interface in Java

March 28, 2023

What is Interface in Java?

Interface in Java Language actually supports multiple inheritance, in contrast to C++. A class can only descend from one other class. Through implements, a class is able to implement numerous interfaces.

An interface may also have constants, static methods, nested interfaces, default methods, and abstract methods.

Interface in Java

Interface in Brief

An Abstract Class called a Java Interface contains a method declaration but not its definition. An interface is implemented by a class in order to inherit abstract methods. An interface may additionally have constants, static methods, nested interfaces, default techniques, and abstract techniques.

It’s equivalent to writing a class to write an interface. However, a class describes an object’s characteristics and actions. Additionally, a class implements the behaviours found in an interface.

Syntax

interface Interface_Name{
       public void method(); //Statements
    }

Implementing Java Interface

The class must implement interface methods since they lack a body before you can access them. All of an interface’s methods must be implemented by the class that implements it.

  • We can ensure the security of implementation without worrying about the implementation component.
  • Several inheritance is not permitted in Java, but you can use interfaces instead because you can create multiple interfaces.
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Example

Run 
interface PrepInsta
{
   public void method1();
   public void method2();
}

class Main implements PrepInsta
{
   public void method1()
   {
	System.out.println("Here is method1 by Interface");
   }
   public void method2()
   {
	System.out.println("Here is method2 by Interface");
   }
   public static void main(String arg[])
   {
	PrepInsta obj = new Main();
	obj.method1();
	obj.method2();
   }
}

Points to Remember:

  • Interfaces cannot be used to construct objects, much like abstract classes.
  • Interface methods lack a body; instead, the “implement” class supplies one.
  • You must override every one of an interface’s methods when implementing it.
  • By default, interface methods are public and abstract.
  • The interface attributes are by default final, static, and public.
  • A constructor cannot be included by an interface.

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