java - Polymorphic arguments work with superclass but not with subclass -

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• what “cannot find symbol” compilation error mean? 7 answers

i learning polymorphism easy on me (literally copying book). try pass class argument method. when can call superclass methods, not actual subclass. using start() method, try make wolf howl:

 public class experiment {     public static void main(string[] args) {         petowner own = new petowner();         own.start();      } }  //trying polymorphic arguments class vet {     public void giveshot(animal a) {         a.howl();     } } class petowner {     public void start() {         vet v = new vet();         wolf w = new wolf();          v.giveshot(w);     } } //inheritance// //kingdom - animal class animal {     public void move() {         system.out.println("*motions softly*");     } } //family - canine class canine extends animal {     public void bark() {         system.out.println("woof!");     } } //species - wolf class wolf extends canine {     public void howl() {         system.out.println("howl! howl!");     } } 

if pass howl method superclass (animal) works fine. if call directly wolf class - works fine. instance doesn't work if try pass wolf class argument , call there.

here why try way, quoted head first java pg 187:

the vet's giveshot() method can take animal give it. long object in argument subclass of animal, work

i getting "cannot find symbol symbol: method howl(), location variable of type animal" error.

you're calling a.howl() while a instance of animal class. animal not know how howl. wolf does.

you can defin method react() , override particular subclass of animal;