Polymorphism and method overloading

Question

I have a quick and straighforward question:

I have this simple class:

public class A
{
    public void m(Object o)
    {
      System.out.println(\"m         


        

Answer 1

Object is the default type in Java. If you refactor your m(Object o) method to m(String o) you'll have a compile time error saying that the call m(null) is ambiguous because Java cannot determine which class between String and Number defaults to null

Other than that, between m(Object o) and m(Number o), calling m(null) will call m(Number o) because it's the most specialized method. You would need to cast null into an Object (or anything not an instance of Number) otherwise.

a.m((String) null);