overloaded methods

[sampath garapati]

class A {}
class B extends A {}
class C extends B {
static void m(A x, A y) {System.out.print("AA");}
static void m(A x, B y) {System.out.print("AB");}
static void m(B x, A y) {System.out.print("BA");}
static void m(B x, B y) {System.out.print("BB");}
public static void main(String[] args) {
A a1; B b1;
m(null,null); m(a1=null,b1=null); m(b1, a1);
}}

In the above program why the output is BBABBA, why not AAABBA

please explain

Thank You Sampath

[Santana Iyer]

class A {}
class B extends A {}
class C extends B {
static void m(A x, A y) {System.out.print("AA");}
static void m(A x, B y) {System.out.print("AB");}
static void m(B x, A y) {System.out.print("BA");}
static void m(B x, B y) {System.out.print("BB");}
public static void main(String[] args) {
A a1; B b1;
m(null,null); m(a1=null,b1=null); m(b1, a1);
}}

I am not 100% sure but as per my evaluation
null can be passed to any reference

so m(null,null) method called is most specific as per hierarchy
next you pass a1,b1 so AB than b1,a1 so BA.

[Akshay Kiran]

Originally posted by Santana Iyer:
so m(null,null) method called is most specific as per hierarchy
next you pass a1,b1 so AB than b1,a1 so BA.

Yes I think thats right, the most specific choice is chosen. However, this is because B is a subclass of A
Suppose you have another class C not related to B, and methods
m(B b1, B b2);
and
m(C c1, C c2);
and call
m(null, null),
the compiler will NOT be able to resolve it and will throw and ambiguous call error.