Why can null be passed to an overloaded Java method? [duplicate]

Question

I found this Java code from this site. I don't understand how it compiles without ambiguous error.

 package swain.test;

 public class Test {
     public static void JavaTest(Object obj) {
         System.out.println("Object");
     }

     public static void JavaTest(String arg) {
         System.out.println("String");
     }

     public static void main(String[] args) {
         JavaTest(null);
     }
}

Output:

String

Answer 1

null can be passed to both JavaTest(String arg) and JavaTest(Object obj), so the compiler chooses the method with the more specific argument types. Since String is more specific than Object (String being a sub-class of Object), JavaTest(String arg) is chosen.

If instead of JavaTest(Object obj) you had JavaTest(Integer obj), the compilation would have failed, since Integer is not more specific than String and String is not more specific thanInteger`, so the compiler wouldn't be able to make a choice.