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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. */