接口

/*Java Interface example.This Java Interface example describes how interface is defined andbeing used in Java language. Syntax of defining java interface is,<modifier> interface <interface-name>{  //members and methods()}*/ //declare an interfaceinterface IntExample{   /*  Syntax to declare method in java interface is,  <modifier> <return-type> methodName(<optional-parameters>);  IMPORTANT : Methods declared in the interface are implicitly public and abstract.  */   public void sayHello();  }/*Classes are extended while interfaces are implemented.To implement an interface use implements keyword.IMPORTANT : A class can extend only one other class, while itcan implement n number of interfaces.*/ public class JavaInterfaceExample implements IntExample{  /*  We have to define the method declared in implemented interface,  or else we have to declare the implementing class as abstract class.  */   public void sayHello(){    System.out.println("Hello Visitor !");  }   public static void main(String args[]){    //create object of the class    JavaInterfaceExample javaInterfaceExample = new JavaInterfaceExample();    //invoke sayHello(), declared in IntExample interface.    javaInterfaceExample.sayHello();  }} /*OUTPUT of the above given Java Interface example would be :Hello Visitor !*/

原文：http://www.java-examples.com/java-interface-example