Instance main method and vararg constructor

[Tagir Valeev]

Hello!

No, I don't think that we should assume any semantics there. Just pass
empty array always. Arguments can be passed to main() method if String[]
args parameter is present, like always.

On Fri, Jul 5, 2024, 17:14 Brian Goetz <brian.goetz at oracle.com> wrote:

> It is reasonable to infer the semantics of a no-arg constructor as “give
> me a default-configured instance of this class”, where default-configured
> is controlled by the class.  This is done by Javabeans, serialization, test
> frameworks, and other frameworks.  But once a constructor has arguments,
> those arguments have semantics.  Can we really assume that a `String…`
> constructor is intended to be used with command-line-argument strings?
> That seems more of a leap.
>
> We do so with `main` because by longstanding convention, `main`
> functions/methods (going back to C) have been associated with the interface
> from the OS launcher to the program.  But I think that’s as far as we
> should take it?
>
> > On Jul 5, 2024, at 11:05 AM, Tagir Valeev <amaembo at gmail.com> wrote:
> >
> > Hello!
> >
> > I wonder if we should enable instance main method if the class has only
> vararg constructor:
> >
> > class Test {
> >   Test(String... data) {
> >   }
> >
> >   void main() {
> >     System.out.println("Hello World!");
> >   }
> > }
> >
> > Java 22 doesn't like it:
> > > \jdks\jdk-22\bin\java.exe --enable-preview Test.java
> > error: can't find no argument constructor in class: Test
> >
> > However, in other contexts, such a class is considered as a class that
> has no-arg constructor. E.g., we can subclass it without explicit
> super-constructor invocation:
> >
> > class Test {
> >   Test(String... data) {
> >   }
> >
> >   static class Use extends Test {}
> > }
> >
> > Would it be consistent to allow launching such classes?
> >
> > With best regards,
> > Tagir Valeev
>
>
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