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NNTP-Posting-Date: Wed, 11 Apr 2012 11:32:38 -0500
Date: Wed, 11 Apr 2012 09:32:31 -0700
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: trigger static init
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On 4/11/2012 8:30 AM, Andreas Leitgeb wrote:
> Patricia Shanahan<pats@acm.org>  wrote:
>> On 4/11/2012 5:52 AM, Andreas Leitgeb wrote:
>>>     T is a top-level class, and an assert statement (§14.10) lexically
>>>             nested within T is executed.
>>> Btw., I don't understand the point about assert. If the assert is
>>> lexically nested in T and gets executed, then I'd have naively thought,
>>> that one of the first two points would necessarily have happened,
>>> anyway, before the assert could be reached. What am I missing here?
>> Suppose S is a static class defined in T. I interpreted that as meaning
>> that executing an assert in S would trigger initialization of T.
>> Or suppose S is non-static, but the assert is in its static code.
>
> I don't yet get it.
>
> === Main.java ===
> public class Main {
>      public static void main(String[] args) {
>          Object foo = new Outer.Inner();
>      }
> }
> class Outer {
>      static {
>          System.out.println("Outer init");
>      }
>      public static class Inner {
>          static {
>              System.out.println("Inner init1");
>              assert 1==1 : "oups!";
>              System.out.println("Inner init2");
>          }
>      }
> }
> === call ===
> $ java -ea Other  ;# ditto without the -ea
> Inner init1
> Inner init2
> $ java -version
> java version "1.6.0_26"
> Java(TM) SE Runtime Environment (build 1.6.0_26-b03)
> Java HotSpot(TM) Server VM (build 20.1-b02, mixed mode)
> $
> === end of SSCCE ===
>
> So, it *is* possible to run code "lexically included in Outer"
> without Outer having been initialized first (which I had wrongly
> believed to be impossible), but assert itself doesn't seem to
> have the specified effect.  I also read §14.10, but that just
> affirms, that (in order to determine the Assertion-flag for the
> toplevel class "Outer") "Outer" would be initialized, too.
> It doesn't seem to happen, though.
>

I may be right about what the JLS comment meant, but it is clear the
implementation is not following it. I enabled assertions, and added a
non-constant assertion that would fail. It still does not initialize
the outer class:

=== Main.java ===
public class Main {
   public static void main(String[] args) {
     Object foo = new Outer.Inner();
     Outer.Inner.innerMethod(5);
   }
}

class Outer {
   static {
     System.out.println("Outer init");
   }

   public static class Inner {
     static {
       System.out.println("Inner init1");
       assert 1 == 1 : "oups!";
       System.out.println("Inner init2");
     }

     static void innerMethod(int arg1) {
       System.out.println("innerMethod 1");
       assert arg1 == 1 : "oops!";
       System.out.println("innerMethod 2");
     }
   }
}
=== call ===
Inner init1
Inner init2
Exception in thread "main" java.lang.AssertionError: oops!
innerMethod 1
	at Outer$Inner.innerMethod(Main.java:22)
	at Main.main(Main.java:4)
=== end of SSCCE ===

Patricia