Unable to solve perfecting prototype challenge

/*  So the age old knock knock joke goes like this:

    Person A:  Knock Knock.
    Person B:  Who's there?
    Person A:  Banana
    Person B:  Banana who?
    ...as long as Person A has answered Banana the above repeats endlessly
    ...assuming the person answers Orange we'd see
    Person B:  Orange who?
    ...and then the punchline.
    Person A:  Orange you glad I didn't say Banana again?
    (It's a really bad joke that makes it sound like "Aren't you glad I didn't say Banana again?")

    Let's just assume the only two words passed in from the console from Person B are either banana or orange.
*/

// ====BEGIN PROMPTING CODE====

// Person A asks:
            String who;
            boolean isBanana;
            do{ 
            console.printf("Knock Knock.\n");
            who = console.readLine("Who's there?  ");
            isBanana = who.equalsIgnoreCase("banana");
                if(isBanana){
                who = console.readLine("%s who?\n", who);
                }
            }while(isBanana);
            console.printf("%s who?\n", who);
            console.printf("%s you glad I didn't say Banana again?",who);
            // ==== END PROMPTING CODE ====
    }

}
// ==== END PROMPTING CODE ====