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Groups > comp.lang.java.programmer > #26644
| From | Robert Klemme <shortcutter@googlemail.com> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Alternatives languages on the JVM: which one or is there no alternative? |
| Date | 2013-11-27 22:57 +0100 |
| Message-ID | <bfn86fF4te5U1@mid.individual.net> (permalink) |
| References | <b61c37c4-1b86-4b63-8ed1-fa5834eb638e@googlegroups.com> <l733pd$7kk$1@Gaia.teknon.de> <bfklnaFis1vU1@mid.individual.net> <l73v2h$f22$1@Gaia.teknon.de> |
On 27.11.2013 06:13, Volker Borchert wrote:
> Robert Klemme wrote:
>> On 26.11.2013 22:28, Volker Borchert wrote:
>>> No language that is to run on the JVM can overcome its fundamental
>>> shortcoming of missing multiple implementation inheritance.
>>
>> I have come to believe that omitting things that other languages do was
>> actually a wise decision of the language designers. Avoiding MI might
>> be one of them. Granted, you cannot use implementation inheritance.
>> But sometimes not making these things easy is actually an advantage. At
>> least I think that when comparing C++ and Java. The equation might
>> calculate differently when comparing Java to other languages (Eiffel?).
>
> Maybe so, but then why did the make multihreading - which is even
> easier to get really wrong - so easy to use...
Probably because MT is necessary given physical limits to what a single
CPU can do.
> OO without MI is like
> a Ford Mustang with a two cylinder two stroke engine. Yes, it might
> eventually take you from A to B, but is it fun?
Why do you use Java if you dislike it so much?
>> Then you need a pair of setters or one setter and one method which
>> switches reference mode. This avoids having two fields and it avoids
>> "lots of duplicated code".
>
> You still have an extra two-word object header, and you cannot use
> WeakReference<T> directly if you want the Foo to act on the
> reference being cleared by garbage collection. These 24 extra bytes
> hurt if you are doing low-level stuff and expect some tens or
> hundreds of thousands of Foo.
It's totally unclear what you mean by "low level stuff".
> Why do you think Java got generally known to be slow and bloated?
Probably because a) computers had less memory and CPU power at the time
it entered the stage and b) the JVM was far less efficient than it is today.
> getItem() above actually checks for assignment compatibility TWICE -
> once for the instanceof and once for the actual cast. JIT should
> mitigate this, but I'd still like to have dynamic_cast
What does dynamic_cast in C++ do differently? As far as I am informed
it involves a type check as well. I mean, you can have the same in Java
by catching the exception (which is what you need to do in C++ IIRC).
>> I do not know your notification requirements but I am sure you are aware
>> of ReferenceQueue.
>
> Yes, of course, but ReferenceQueue.poll() returns the Reference<T>,
> not the Foo, so for the Foo to act, you need something like
>
> class Foo<T> {
> // nonstatic inner class uzes 4 bytes for the
> // implicit this$0 and 4 more bytes padding
> class TPtr<T> extends WeakReference<T> {
> Foo foo() {
> return Foo.this;
> }
> }
>
> void gced() {
> }
> }
Since Foo inherits Object you could as well make Foo<T> inherit
WeakReference<T> avoiding the additional bytes per instance. And it's
basically what Foo seems to be: a reference to a T - so it's actually
not too far fetched.
> to do something like
>
> ...
> while ((ref = queue.poll()) != null) {
> ((TPtr<T>) ref).foo().gced();
> }
> ...
What does that thread do outside this loop?
>> How do you do that? The only way I can think of is
>> having an additional thread blocking in ReferenceQueue.remove().
>
> BTDT
And why did it not work for you?
>> wouldn't it make more sense to let T know of its container / owner?
>
> Why? What for?
Since Foo references the other object there seems to be a business
relationship between the two. T would then need to be bound by an
interface.
I find it difficult to discuss this without knowing more about your
requirements and situation. But then again, maybe you don't want or
cannot disclose that.
Cheers
robert
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
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Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-25 03:09 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-25 12:46 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-25 05:20 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-25 22:10 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-25 14:34 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-26 08:54 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-26 00:29 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-26 15:29 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Arne Vajhøj <arne@vajhoej.dk> - 2013-11-26 21:55 -0500
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-27 08:59 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Joerg Meier <joergmmeier@arcor.de> - 2013-11-27 10:41 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-28 12:48 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? leif.roar@invalid.com (Leif Roar Moldskred) - 2013-11-28 16:28 -0600
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-29 00:03 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-29 00:41 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-29 12:05 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-29 03:51 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-29 16:44 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-29 16:48 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-12-02 06:33 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-02 15:50 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-02 16:26 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-12-02 21:07 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-02 23:33 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? markspace <markspace@nospam.nospam> - 2013-12-02 18:07 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-03 08:59 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-12-03 00:14 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-03 09:42 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-12-03 02:58 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Martin Gregorie <martin@address-in-sig.invalid> - 2013-12-03 20:55 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-12-04 00:12 -0800
Re: Alternatives languages on the JVM: which one or is there no alternative? Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-12-14 03:31 -0400
Re: Alternatives languages on the JVM: which one or is there no alternative? Martin Gregorie <martin@address-in-sig.invalid> - 2013-12-14 10:11 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-12-14 17:39 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2013-12-14 16:52 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-12-14 13:47 -0400
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-12-14 23:55 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Sebastian <news@seyweiler.dyndns.org> - 2013-12-04 10:39 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-12-14 03:56 -0400
Re: Alternatives languages on the JVM: which one or is there no alternative? v_borchert@despammed.com (Volker Borchert) - 2013-11-26 21:28 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-26 23:29 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? v_borchert@despammed.com (Volker Borchert) - 2013-11-27 05:13 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-27 22:57 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? v_borchert@despammed.com (Volker Borchert) - 2013-11-29 23:22 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-30 14:41 +0100
Re: Alternatives languages on the JVM: which one or is there no alternative? Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2013-11-30 16:49 -0600
Re: Alternatives languages on the JVM: which one or is there no alternative? Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2013-11-27 23:07 -0600
Re: Alternatives languages on the JVM: which one or is there no alternative? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-11-28 23:41 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2013-11-29 00:08 -0600
Re: Alternatives languages on the JVM: which one or is there no alternative? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-11-29 16:49 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2013-11-30 16:46 -0600
Re: Alternatives languages on the JVM: which one or is there no alternative? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2014-02-14 15:36 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? v_borchert@despammed.com (Volker Borchert) - 2013-11-29 23:37 +0000
Re: Alternatives languages on the JVM: which one or is there no alternative? Roedy Green <see_website@mindprod.com.invalid> - 2013-11-28 12:50 -0800
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