[Fwd: Re: invokevirtual #3 ]

[Andreas Schlapbach <sc...@iam.unibe.ch>]

This is the explaination for <method null> I got asking some time ago on
a newsgroup.

Andreas

> ---------------------------------------------------------------------
> JLS 13
> requires that compilers emit method references relative to the class
> that qualifies the method invocation, even if that class only inherits
> the method.  It is then up to the VM to correctly track inheritance
> issues when resolving method calls.  Sun's javac 1.3 also had this bug,
> JDK 1.4 compiles the way jikes 1.15a does (ie. Encoder8859_1.loadTable).
>
> It makes a difference in this example:
>
> in A.java:
> class A
> {
>   static void m() { System.out.print("a"); }
> }
>
> in B.java:
> class B extends A {}
>
> in C.java:
> class C
> {
>   public static void main(String[] args)
>   {
>     B.m();
>   }
> }
>
> Now, recompile B.java:
> class B extends A
> {
>   static void m() { System.out.print("b"); }
> }
>
> The result of executing the (unchanged) C.class should now be "b", not
> "a".
>
> This is also the reason that Sun's javap program will often list null as
> the method or field name for classes compiled with javac 1.4, because
> they have not yet fixed javap to take inheritance into account.


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