Ambiguous method

Re: Ambiguous method

Laurent Thery wrote:
[color=blue]
> Given the following example:
>
> =============== =============== ==============
>
> class A {
> int method (B a) {
> return 1;
> }
> }
> class B extends A {
> int method (A b) {
> return 2;
> }
> }
> class Test {
> public static void main(String[] args) {
> System.out.prin tln(new B().method(new B()));
> }
> }
>
> =============== =============== ===============
>
> When compiling with 1.4.1_02, the compiler is complaining with:
>
> Test.java:13: reference to method is ambiguous, both method method(B)
> in A and method method(A) in B match
> System.out.prin tln(new B().method(new B()));
>
> When compiling with 1.4.2, the compiler is happy and the program
> returns 1
>
>
> It seems that something has changed with 1.4.2. Unfortunately I could
> not find anything in the changes.
> Anybody can explain me what has exactly changed with method selection
>
> Thanks
>
> --
> Laurent Thery[/color]

I'm no expert, but that smacks of a compiler bug to me.

Re: Ambiguous method

thery@sophia.in ria.fr (Laurent Thery) wrote:[color=blue]
> [snipped example]
>
> When compiling with 1.4.1_02, the compiler is complaining with:
>
> Test.java:13: reference to method is ambiguous, both method method(B)
> in A and method method(A) in B match
> System.out.prin tln(new B().method(new B()));
>
> When compiling with 1.4.2, the compiler is happy and the program
> returns 1
>
>
> It seems that something has changed with 1.4.2. Unfortunately I could
> not find anything in the changes.
> Anybody can explain me what has exactly changed with method selection[/color]

This is due to a change in the Java2 Language Specification. Check out
http://java.sun.com/docs/books/jls/c...-2-2nd-ed.html with
an eye on Section 15.12.2.2. The original specification, used by
1.4.1, said that both the type of the class that the method was
defined in, and the type of the arguments, were considered when trying
to determine the "maximally specific" method. The new specification,
used in 1.4.2, only considers the types of the arguments.

See also the original problem report at


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