in java null value in String

Question

I get a compilation error at prt(null) in the following:

 public class Abc {

    public static void prt(String b)
    {
        System.out.println("I m static Method with String");
    }
    public static void prt(Abc n)
    {
        System.out.println("I m static Method with Object");
    }


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

    }

}

but this class is fine:

public class Abc {

    public static void prt(String b)
    {
        System.out.println("I m static Method with String");
    }
    public static void prt(Object n)
    {
        System.out.println("I m static Method with Object");
    }


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

    }

}

Please help me understand null value in String, in any class object and in Object class object.

Answer 1

You should read carefully full compiler message. Its probably complains that the call prt(null) is ambiguous. In fact you should typecast it: prt((String)null) or prt((Abc)null) to let compiler know what parameter overloaded method to call.

Quote to explore:

It will call the method whose parameter type is a subclass of the parameter type of the other method. Beware! The parameter type is defined by the declared type of an object, not its instantiated type.