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Q) How to define a method if its return type is interface type?




A)
->in the child method create any child class object of that interface and return its reference.

//test.java

interface servletrequest
{
       void getUserInput();
}
interface servletresponse
{
       voidgiveresponsetouser();
}
class TomcatServletRequest implements servletrequest
{
       public void getUserInput()
       {
              System.out.println("getting user input nicely");
       }
}
classTomcatservletresponse implements servletresponse
{
       public void giveresponsetouser()
       {
              System.out.println("giving user output nicely");
       }
}
classweblogicservletrequest implements servletrequest
{
       public void getUserInput()
       {
              System.out.println("getting user input excelently");
       }
}
classweblogicservletresponse implements servletresponse
{
       public void giveresponsetouser()
       {
              System.out.println("giving output to user excelently");
       }
}
class MyServlet
{
       void service (servletrequest request, servletresponse response)
       {
              request.getUserInput();
              response.giveresponsetouser();
       }//user defined method.that takes interface objects as arguments.
}
class test1
{
       public static void main(String args[])
       {
              MyServlet myservelet=new MyServlet();
              servletrequest request = new weblogicservletrequest();
              servletresponse response= new weblogicservletresponse();
              myservelet.service(request,response);
             
       }
}

Output:

getting user input excelently
giving output to user excellently

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