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Groups > comp.lang.java.programmer > #15386

Re: "Small" Program Challenge.

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On Monday, June 18, 2012 9:04:15 AM UTC-7, Daniel Pitts wrote:
> On 6/17/12 9:25 PM, Lew wrote:
> > On 06/17/2012 08:40 PM, Daniel Pitts wrote:
> >> On 6/17/12 5:55 PM, javax.swing.JSnarker wrote:
> >>> On 17/06/2012 8:31 PM, Arne Vajhøj wrote:
> >>>> On 6/17/2012 6:25 PM, javax.swing.JSnarker wrote:
> >>>>> On 17/06/2012 6:24 PM, Daniel Pitts wrote:
> >>>>>> I will post my solution, once everyone else has had a chance to
> >>>>>> attempt
> >>>>>> the problem.
> >>>>>
> >>>>> "Everyone else"? As in, all seven billion of us?!
> >>>>
> >>>> In theory if he wait X days, then a good chunk of those 7 B would
> >>>> have had a chance to go on the internet, read and reply.
> >>>>
> >>>> In practice it will be a very small subset, but ...
> >>>
> >>> The problem is, he said "everyone else" rather than "almost everyone
> >>> else". So "a good chunk" won't cut it.
> >>>
> >> Well, while you took me literally, my intent was to wait "for enough
> >> people
> >> that wished to contribute to this conversation to do so."
> >>
> >> Or for someone to find the same (or better) solution.
> >>
> >> I suppose that a date deadline would have been more appropriate.
> >>
> >> In any case, I think the other challenge was more interesting. My
> >> solution to
> >> the "shortest" source is 60 characters long. The first two lines are
> >> simply a
> >> ruler, and not part of the source code.
> >>
> >> 1 2 3 4 4 6
> >> 123456789012345678901234567890123456789012345678901234567890
> >> enum H{W;System s;{s.out.println("Hello World");s.exit(0);}}
> >>
> >> You would compile whatever file H was in (it needn't be in H.java
> >> since it
> >> isn't public). Then execute with "java H"
> >>
> >> Note, this no longer works in Java 7. It appears a method with the
> >> signature
> >> "public static void main(String[])" is now required, where it could
> >> have been
> >> omitted in the past (as in my example).
> >
> > You aren't supposed to rely on a bug.
> >
> > The JLS 3rd ed., which covers Java 5 and Java 6, says,
> > "A Java virtual machine starts up by loading a specified class and then
> > invoking the method main in this specified class."
> > <http://docs.oracle.com/javase/specs/jls/se5.0/html/execution.html>
> My program wasn't a bug, it relied on loading the specified class, which 
> has the (documented) side-effect of initializing the class, which causes 
> the initializers to run.

Not true.

> > and
> > "A Java virtual machine starts execution by invoking the method main of
> > some specified class, passing it a single argument, which is an array of
> > strings."
> > <http://docs.oracle.com/javase/specs/jls/se5.0/html/execution.html#44444>
> >
> > If you got it to start a different way, that was unreliable behavior and
> > not actually correct.
> The wording in the 3rd edition is different enough to explain the 

How, exactly?

> difference in behavior, and so Java 6 in fact has the required behavior 
> of loading the class.  Java 7 doesn't require the class be loaded before 
> invoking the method.

Java never required initialization upon load, and in fact was very specific about 
the circumstances under which a class initializes.

<http://docs.oracle.com/javase/specs/jls/se5.0/html/execution.html#12.4.1>
"A class or interface type T will be initialized immediately before the first occurrence of any one of the following:

- T is a class and an instance of T is created.
- T is a class and a static method declared by T is invoked.
- A static field declared by T is assigned.
- A static field declared by T is used and the field is not a constant variable (§4.12.4).
- T is a top-level class, and an assert statement (§14.10) lexically nested within T is executed.

Invocation of certain reflective methods in class Class and in package java.lang.reflect also 
causes class or interface initialization. A class or interface will not be initialized under any 
other circumstance."

You are saying that the first case applies, an instance is created because of 
the third case, a static field is assigned. But that assignment shouldn't happen 
yet because nothing has invoked the class legally, i.e., the sequence to invoke 
'main()' didn't happen. It is, in fact, the invocation of 'main()' that is supposed to 
trigger the initialization.

Historically Sun's JVMs have had bugs in this area, by their own admission.

I read the JLS 3rd edition as not allowing the behavior you claim as a solution.
There has been no change in the language regarding how a JVM starts.

So if the trick violates Java 7, and the language hasn't changed, it must also violate
Java 6, and that it worked was a bug.

Perhaps if you could quote the exact differences in wording to which you refer?

-- 
Lew

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Thread

"Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-13 13:45 -0700
  Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-13 13:52 -0700
    Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-13 16:17 -0700
      Re: "Small" Program Challenge. glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-06-14 00:16 +0000
    Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-13 16:19 -0700
      Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-13 16:24 -0700
    Re: "Small" Program Challenge. markspace <-@.> - 2012-06-13 17:40 -0700
  Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-13 21:28 -0400
  Re: "Small" Program Challenge. Roedy Green <see_website@mindprod.com.invalid> - 2012-06-13 20:52 -0700
    Re: "Small" Program Challenge. "Hiram Hunt" <hiramhunt@verizon.net> - 2012-06-14 08:23 -0400
      Re: "Small" Program Challenge. "Hiram Hunt" <hiramhunt@verizon.net> - 2012-06-14 08:30 -0400
    Re: "Small" Program Challenge. Arne Vajhøj <arne@vajhoej.dk> - 2012-06-17 21:17 -0400
  Re: "Small" Program Challenge. Paul Cager <paul.cager@googlemail.com> - 2012-06-14 02:32 -0700
  Re: "Small" Program Challenge. Bent C Dalager <bcd@pvv.ntnu.no> - 2012-06-14 11:29 +0000
  Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-14 12:50 -0700
  Re: "Small" Program Challenge. Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-06-14 15:49 -0500
  Re: "Small" Program Challenge. Gene Wirchenko <genew@ocis.net> - 2012-06-14 14:56 -0700
  Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-14 17:02 -0700
  Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-14 17:09 -0700
  Re: "Small" Program Challenge. Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2012-06-15 22:13 -0700
    Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-16 12:11 -0700
  Re: "Small" Program Challenge. Wanja Gayk <brixomatic@yahoo.com> - 2012-06-17 15:22 +0200
    Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-17 15:24 -0700
      Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-17 18:25 -0400
        Re: "Small" Program Challenge. Arne Vajhøj <arne@vajhoej.dk> - 2012-06-17 20:31 -0400
          Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-17 20:55 -0400
            Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-17 20:40 -0700
              Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-17 23:43 -0400
              Re: "Small" Program Challenge. Lew <noone@lewscanon.com> - 2012-06-17 21:25 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 00:45 -0400
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-18 12:47 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 15:57 -0400
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-18 13:31 -0700
                Re: "Small" Program Challenge. Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-06-18 16:05 -0500
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-18 14:18 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 19:50 -0400
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 19:48 -0400
                Re: "Small" Program Challenge. David Lamb <dalamb@cs.queensu.ca> - 2012-06-19 08:07 -0400
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-19 15:26 -0400
                Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-18 09:04 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 13:09 -0400
                Re: "Small" Program Challenge. markspace <-@.> - 2012-06-18 11:06 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 14:46 -0400
                Re: "Small" Program Challenge. markspace <-@.> - 2012-06-18 13:22 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 19:51 -0400
                Re: "Small" Program Challenge. Wanja Gayk <brixomatic@yahoo.com> - 2012-06-20 13:11 +0200
                Re: "Small" Program Challenge. Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-06-22 12:54 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-22 18:30 -0400
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-25 12:59 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-25 16:49 -0400
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-18 12:44 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 16:01 -0400
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-18 13:36 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 20:01 -0400
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-18 18:25 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 22:01 -0400
                Re: "Small" Program Challenge. Gene Wirchenko <genew@ocis.net> - 2012-06-18 19:04 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-18 22:12 -0400
                Re: "Small" Program Challenge. Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-06-19 12:36 +0000
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-19 15:28 -0400
                Re: "Small" Program Challenge. Gene Wirchenko <genew@ocis.net> - 2012-06-19 09:12 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-19 15:30 -0400
                Re: "Small" Program Challenge. Gene Wirchenko <genew@ocis.net> - 2012-06-19 15:04 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-19 18:23 -0400
                Re: "Small" Program Challenge. Gene Wirchenko <genew@ocis.net> - 2012-06-19 15:32 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-19 19:09 -0400
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-19 19:10 -0400
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-19 17:19 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-19 20:42 -0400
                Re: "Small" Program Challenge. Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-06-19 20:01 -0500
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-19 21:12 -0400
                Re: "Small" Program Challenge. Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-06-19 20:32 -0500
                Re: "Small" Program Challenge. Lew <noone@lewscanon.com> - 2012-06-19 22:01 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-20 21:15 -0400
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-20 21:05 -0400
                Re: "Small" Program Challenge. Wanja Gayk <brixomatic@yahoo.com> - 2012-06-23 13:42 +0200
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-23 12:12 -0400
                Re: "Small" Program Challenge. Wanja Gayk <brixomatic@yahoo.com> - 2012-06-23 23:10 +0200
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-23 17:14 -0400
                Re: "Small" Program Challenge. Lew <noone@lewscanon.com> - 2012-06-19 22:15 -0700
                Re: "Small" Program Challenge. Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-06-20 10:34 +0000
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-20 10:45 -0700
                Re: "Small" Program Challenge. Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2012-06-21 08:13 +0000
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-21 17:18 -0400
                Re: "Small" Program Challenge. Lew <lewbloch@gmail.com> - 2012-06-21 15:30 -0700
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-21 20:28 -0400
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-20 21:22 -0400
                Re: "Small" Program Challenge. "javax.swing.JSnarker" <gharriman@boojum.mit.edu> - 2012-06-20 21:19 -0400

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