Dynamic binding problem

Question

I have a problem, i want to use a extend to arraylist to implement different validation to objects. So i added a method add(Person person), dynamic binding, but it has a incorrect behavior, i think
import java.util.ArrayList;
import java.util.Collection;
public class Test {
     class MyList extends ArrayList {
          public boolean add(Object arg0) {
               System.out.println("add norm");
               return super.add(arg0);
          public boolean add(Person arg0) {
               System.out.println("add person");
               return super.add(arg0);
     class Person{
     public static void main(String[] args) {
          new Test().test();
     private void test() {
          Collection col1 = new MyList();
          col1.add(new Person());
          ArrayList col2 = new MyList();
          col2.add(new Person());
          MyList col3 = new MyList();
          col3.add(new Person());
}My output=
add norm
add norm
add person
My wanted output
add person
add person
add person
Why?

Answer 1

in case you don't understand why you're getting "addning norm"
you are using polymorphism. You declared your objects to be of type Collection and ArrayList. This means you can only use methods of those type, eventhough the underlying object is a MyList instance. Now, Collections and ArrayList class only have the add(Object obj) method signature....so, when you say add(new Person()), it will only see add(Object obj)
When you declared your object as MyList, then it see add(Person p), so it use the add(Person p) method.