On Thu, 19 Mar 2026 15:15:29 GMT, Jan Lahoda <[email protected]> wrote:
>> I just gave this a try against Java 26:
>>
>>
>> public class BaseClass {
>> public void main() {
>> System.out.println("hello from " + BaseClass.class);
>> }
>> }
>>
>>
>>
>> public class ChildClass extends BaseClass {
>> public native void main();
>> }
>>
>>
>> Then compiled them:
>>
>>
>> javac BaseClass.java ChildClass.java
>>
>>
>> and launched the `ChildClass`:
>>
>>
>> java ChildClass
>>
>> This fails with:
>>
>>
>> Exception in thread "main" java.lang.UnsatisfiedLinkError: 'void
>> ChildClass.main()'
>> at ChildClass.main(Native Method)
>>
>>
>> which I think is wrong, and instead the `java` launcher should have picked
>> up `BaseClass.main()` as the main entry point?
>
> Thanks for the comment. First, let me point out that the `main` method
> selection is not up to the launcher to decide. The selection process is
> specified by the JLS:
> https://docs.oracle.com/javase/specs/jls/se26/html/jls-12.html#jls-12.1.4
> and the specification to my knowledge says nothing about `native` or
> `abstract` in terms of selection.
>
> Specifically for `native`, I don't see why the selection should ignore
> `native` methods. Those can be invoked (provided the native library is
> correctly linked in, of course). Additionally, note that in your example, the
> method `BaseClass.main()` is not even a member of `ChildClass`, as
> `ChildClass` overrides the method, making it even more difficult to call
> `BaseClass.main()` in context of `ChildClass`.
>
> For `abstract`, admittedly, the selection process may select an abstract
> method, while there may be an alternative static method it could call, like
> here:
>
> $ cat /tmp/M.java
> public abstract class M {
> abstract void main(String... args);
> static void main() {
> System.err.println("Hello!");
> }
> }
> $ javac /tmp/M.java
> $ java -classpath /tmp/ M
> Error: abstract class M can not be instantiated
> please use a concrete class
>
>
> But, I think this is very consistent with what the JLS is saying about the
> selection. Discussion on whether the selection process in JLS should be
> different is possible, but an implementation PR is not the best venue for it.
I agree, this needs clarification in the specification.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/30221#discussion_r2966326742
