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Groups > comp.lang.java.programmer > #33783
| Newsgroups | comp.lang.java.programmer |
|---|---|
| Date | 2016-02-11 15:45 -0800 |
| References | (11 earlier) <56bcaad1$0$23816$e4fe514c@news.xs4all.nl> <n9iei6$sbr$1@dont-email.me> <56bccc91$0$23792$e4fe514c@news.xs4all.nl> <n9iq9g$f95$1@dont-email.me> <56bd10d2$0$23750$e4fe514c@news.xs4all.nl> |
| Message-ID | <9e042cbd-0f26-406a-8d98-8abcc4bdc7e4@googlegroups.com> (permalink) |
| Subject | Re: Java Checked Exception is BAD! |
| From | Lew <lewbloch@gmail.com> |
On Thursday, February 11, 2016 at 2:53:47 PM UTC-8, Silvio wrote:
> On 02/11/2016 09:20 PM, Eric Sosman wrote:
> >
> > Again, lambda expressions just produce classes that implement
> > interfaces (and yield references to methods of those classes). If
> > the interface declares its abstract method with no `throws', the
> > lambda body must not throw an IOException. But if the interface
> > says `throws IOException' you're fine.
> >
> > An interface can say `throws Exception' or even `throws Throwable',
> > but it seems to me those are cop-outs.
> >
> > I do not understand what you mean by "second class" here. As far
> > as I can see, the only "new" thing about lambda expressions (beyond
> > the syntax) is the fact that they yield method references, something
> > Java didn't offer until recently. These are almost equivalent:
> >
> > Set<String> newWay = new TreeSet<>((p,q) ->
> > p.toLowerCase().compareTo(q.toLowerCase));
> >
> > Set<String> oldWay = new TreeSet<>(new Comparator() {
> > @Override
> > public int compare(String p, String q) {
> > return p.toLowerCase().compareto(q.toLowerCase());
> > }
> > });
> >
>
> Yes, you are totally correct. That is how lambdas are defined in Java.
>
> I call them second class citizens here because they have no inherent
> type. Their type is deduced from the expected type at the location they
> occur so they are coerced into an instance of a synthetic class
> compatible with that expected type. That indeed reduces them to little
> more than a shorthand for local classes. That line of reasoning makes
> the limitation that a lambda can not modify local state and must conform
> to the normal checked exception rules seem no more than logical.
>
> I suspect part of the reason for doing it this way was the desire to
> make lambdas compatible with classes and methods in the existing runtime
> library without changing them. Like being able to use a lambda wherever
> a Runnable value is expected.
>
> To me it seems like they came up with the brilliant idea to add actual
> closures to Java and in the end settled on what we now call lambdas.
It was a wellspring of demand from the programmer community that sparked the addition.
At no point really did the Java Godparents actually consider full first-class functions, or closures.
> Perhaps because it would take too much effort to do actual closures,
> perhaps because of backward compatibility issues, perhaps because they
The stated reasons were backward compatibility and to minimize the ramp-up for developers.
> feared the Java world would consider them too foreign, perhaps because
Nonsense. The "Java world" was all agog over closures, and wanted them so badly they forced Java to change.
I watched it happen, in these very forums.
> they just did not fit in nicely with things like checked exceptions
> without adding substantial complexity to the existing language.
>
> >
> > There is no reduction, not as far as I can see, and certainly
> > not because of checked exceptions. The interface describes what (if
> > any) exceptions are permitted, and the lambda expression is no more
> > (or less) limited than an ordinary class would be.
> >
> >> [...]
> >> I realize that lambdas did not exist when checked exceptions where put
> >> into the language. And I also agree that it is not at all black or
> >> white. Checked exceptions have advantages as well as disadvantages. What
> >> weighs stronger is partly a matter of taste. But the way they limit
> >> lambdas most definitely weighs against them.
Perhaps one should not declare checked exceptions in the overridden method of lambdas, then.
> > What additional "limit" do checked exceptions place on lambda
> > expressions that they do not also place on ordinary classes that
> > implement the same interface? I'm not seeing it.
> >
>
> As long as you look at a lambda as no more than a shorthand for an
> ordinary class that is to be expected. Look at what can be done with
> closures in other languages, Scala for example, and you may see my point.
Other languages are beside the point. Java never claimed to have closures in full. Lambdas were billed initially as a notational convenience for SAM (Single-Abstract-Method) interfaces (after competing with other ideas). Since then, what with streams and the :: notation, they've become a rather powerful and useful construct. Far more so than I expected when it was first discussed.
> And you would be right that such is not impossible with checked
> exceptions. I just do not think any language should want to have so
> complex a type system as would be required to make that work.
Checked exceptions, like most code idioms, are subject to abuse, especially by people who don't understand exceptions or the rationale for including them in a method signature. It is not mandatory to use them in your API - many APIs use only runtime exceptions. Of course, those also carry risk, due to the very fact that they are not part of the method signature.
Exceptions generally, not just checked exceptions, pose issues for anonymous classes and lambdas generally. We just have to be smart about understanding our programming language, and how we use it.
--
Lew
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Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 07:18 -0800
Re: Java Checked Exception is BAD! Eric Douglas <e.d.programmer@gmail.com> - 2016-02-04 08:15 -0800
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-04 17:57 +0100
Re: Java Checked Exception is BAD! Eric Douglas <e.d.programmer@gmail.com> - 2016-02-04 10:09 -0800
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-04 21:01 +0100
Re: Java Checked Exception is BAD! Eric Douglas <e.d.programmer@gmail.com> - 2016-02-04 12:14 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-04 15:16 -0500
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-04 21:37 +0100
Re: Java Checked Exception is BAD! Eric Douglas <e.d.programmer@gmail.com> - 2016-02-04 13:08 -0800
Re: Java Checked Exception is BAD! 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-04 21:16 +0000
Re: Java Checked Exception is BAD! Eric Douglas <e.d.programmer@gmail.com> - 2016-02-04 13:28 -0800
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-04 23:11 +0000
Re: Java Checked Exception is BAD! a.laforgia@gmail.com - 2016-02-05 04:21 -0800
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-05 13:07 +0000
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-04 18:04 -0500
Re: Java Checked Exception is BAD! Gene Wirchenko <genew@telus.net> - 2016-02-05 11:40 -0800
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-04 23:22 +0100
Re: Java Checked Exception is BAD! ruben <ceo@iran.gov> - 2016-02-15 11:45 +0000
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 11:57 -0800
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-04 21:07 +0100
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 11:10 -0800
Re: Java Checked Exception is BAD! Eric Douglas <e.d.programmer@gmail.com> - 2016-02-04 11:28 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 11:33 -0800
Re: Java Checked Exception is BAD! 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-04 21:08 +0000
Re: Java Checked Exception is BAD! Lew <lewbloch@gmail.com> - 2016-02-04 16:09 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-04 12:00 -0500
Re: Java Checked Exception is BAD! Marcel Mueller <news.5.maazl@spamgourmet.org> - 2016-02-04 19:28 +0100
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 11:15 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-04 14:51 -0500
Re: Java Checked Exception is BAD! 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-04 21:07 +0000
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 14:36 -0800
Re: Java Checked Exception is BAD! a.laforgia@gmail.com - 2016-02-05 05:28 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 15:31 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-05 08:20 -0500
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-05 08:25 -0800
Re: Java Checked Exception is BAD! Eric Douglas <e.d.programmer@gmail.com> - 2016-02-05 08:47 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-05 16:09 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-06 08:38 -0500
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-06 14:13 +0000
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-06 15:23 +0100
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-07 14:49 +0100
Re: Java Checked Exceptions Robert Klemme <shortcutter@googlemail.com> - 2016-02-07 21:55 +0100
Re: Java Checked Exceptions boxzou@gmail.com - 2016-02-07 14:39 -0800
Re: Java Checked Exceptions Robert Klemme <shortcutter@googlemail.com> - 2016-02-08 13:30 +0100
Re: Java Checked Exceptions boxzou@gmail.com - 2016-02-08 06:14 -0800
Re: Java Checked Exceptions Robert Klemme <shortcutter@googlemail.com> - 2016-02-08 20:55 +0100
Re: Java Checked Exceptions Lew <lewbloch@gmail.com> - 2016-02-08 16:06 -0800
Re: Java Checked Exceptions boxzou@gmail.com - 2016-02-08 18:38 -0800
Re: Java Checked Exceptions Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-09 12:15 +0000
Re: Java Checked Exceptions boxzou@gmail.com - 2016-02-09 04:59 -0800
Re: Java Checked Exceptions Lew <lewbloch@gmail.com> - 2016-02-10 12:13 -0800
Re: Java Checked Exceptions boxzou@gmail.com - 2016-02-10 19:00 -0800
Re: Java Checked Exceptions Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-11 12:18 +0000
Re: Java Checked Exceptions leif.roar@dimnakorr.com - 2016-02-11 04:43 -0600
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 14:34 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 14:11 -0800
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-07 23:19 +0000
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 15:42 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-06 09:43 -0500
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 14:14 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-08 09:22 -0500
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-08 11:01 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-08 11:08 -0800
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-08 22:02 +0100
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 14:09 -0800
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-07 23:29 +0000
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-08 21:49 +0100
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-08 17:23 -0500
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-08 18:46 -0800
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-09 08:21 +0100
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-09 04:58 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-09 08:17 -0500
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-09 07:57 -0800
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-10 02:37 +0100
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-10 18:58 -0800
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-11 08:13 -0500
Re: Java Checked Exception is BAD! Lew <lewbloch@gmail.com> - 2016-02-11 14:02 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-11 16:41 -0800
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-10 02:31 +0100
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-10 18:47 -0800
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-09 12:26 +0000
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-09 04:57 -0800
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-09 18:27 +0000
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 20:19 -0800
Re: Java Checked Exception is BAD! Robert Klemme <shortcutter@googlemail.com> - 2016-02-06 16:01 +0100
Re: Java Checked Exception is BAD! 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-06 15:10 +0000
Re: Java Checked Exception is BAD! Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2016-02-06 17:59 -0800
Re: Java Checked Exception is BAD! 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-07 09:34 +0000
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 14:23 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 20:52 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 21:13 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-07 14:19 -0800
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-07 23:42 +0000
Re: Java Checked Exception is BAD! Robert Klemme <shortcutter@googlemail.com> - 2016-02-08 13:17 +0100
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-08 04:39 -0800
Re: Java Checked Exception is BAD! Lew <lewbloch@gmail.com> - 2016-02-08 16:05 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-08 18:35 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-08 19:10 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-08 19:12 -0800
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-11 16:37 +0100
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-11 12:00 -0500
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-11 19:01 +0100
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-11 20:32 +0100
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-11 15:20 -0500
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-11 23:53 +0100
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-11 18:21 -0500
Re: Java Checked Exception is BAD! Lew <lewbloch@gmail.com> - 2016-02-11 15:45 -0800
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-12 01:19 +0100
Re: Java Checked Exception is BAD! Lew <lewbloch@gmail.com> - 2016-02-11 19:18 -0800
Re: Java Checked Exception is BAD! Sebastian <news@seyweiler.dyndns.org> - 2016-02-12 08:31 +0100
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-12 15:33 +0100
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-12 15:41 +0100
Re: Java Checked Exception is BAD! Silvio <silvio@internet.com> - 2016-02-12 15:42 +0100
Re: Java Checked Exception is BAD! Martin Gregorie <martin@address-in-sig.invalid> - 2016-02-08 21:19 +0000
Re: Java Checked Exception is BAD! Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-02-05 13:00 -0500
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 15:51 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 15:59 -0800
Re: Java Checked Exception is BAD! boxzou@gmail.com - 2016-02-04 16:03 -0800
Re: Java Checked Exception is BAD! Eric Douglas <e.d.programmer@gmail.com> - 2016-02-05 05:33 -0800
Re: Java Checked Exception is BAD! Kevin McMurtrie <mcmurtrie@pixelmemory.us> - 2016-02-04 21:05 -0800
Re: Java Checked Exception is BAD! ynseo <yeori.seo@gmail.com> - 2016-02-08 01:05 -0800
Re: Java Checked Exception is BAD! Sebastian <sebastian.millies@softwareag.com> - 2016-02-19 03:43 -0800
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