Interface in Java
Interface can have only abstract methods. Since Java 8, it can have default and static methods.
All methods are by-default public.
Interface has only public, static and final variables.
Interface can't have constructor.
Following modifiers can't be applied to the methods declared in an interface :-
private, protected, final, synchronized.
Use interface keyword to declare interface.
Exampl :
interface Animal { public void talk(); } class Dog implements Animal { public void talk(){ System.out.println("bark"); } } class Cat implements Animal { public void talk(){ System.out.println("mew"); } } class MainClass { public static void main(String[] ar){ Animal ob = new Dog(); ob.talk(); Animal ob1 = new Cat(); ob1.talk(); } }OUTPUT :
bark mew
An interface can extends one or more interface.
interface A{ } interface B extends A{ } interface C extends A, B {}
One or more interfaces can be implemented in a class.
interface A{ } interface B{ } class Test implements A, B{ }
A class can extends one class and implements one ore more interfaces at the same time, but class will extends first and then implements interface.
interface A{ } class B{ } class Test extends B implements A{ }
Next topic is object-cloning
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