Java Interface Example

1. /*
2. Java Interface example.
3. This Java Interface example describes how interface is defined and
4. being used in Java language.
5.  
6. Syntax of defining java interface is,
7. <modifier> interface <interface-name>{
8.   //members and methods()
9. }
10. */
11.  
12. //declare an interface
13. interface IntExample{
14.  
15.   /*
16.   Syntax to declare method in java interface is,
17.   <modifier> <return-type> methodName(<optional-parameters>);
18.   IMPORTANT : Methods declared in the interface are implicitly public and abstract.
19.   */
20.  
21.   public void sayHello();
22.   }
23. }
24. /*
25. Classes are extended while interfaces are implemented.
26. To implement an interface use implements keyword.
27. IMPORTANT : A class can extend only one other class, while it
28. can implement n number of interfaces.
29. */
30.  
31. public class JavaInterfaceExample implements IntExample{
32.   /*
33.   We have to define the method declared in implemented interface,
34.   or else we have to declare the implementing class as abstract class.
35.   */
36.  
37.   public void sayHello(){
38.     System.out.println("Hello Visitor !");
39.   }
40.  
41.   public static void main(String args[]){
42.     //create object of the class
43.     JavaInterfaceExample javaInterfaceExample = new JavaInterfaceExample();
44.     //invoke sayHello(), declared in IntExample interface.
45.     javaInterfaceExample.sayHello();
46.   }
47. }
48.  
49. /*
50. OUTPUT of the above given Java Interface example would be :
51. Hello Visitor !
52. */