All points well taken -- at least by me.
I know what it's like to work as hard as you can towards something and
be shot down by criticism that you're not doing anything or not even trying.
That said, a few points:
* Not all of us are compiler experts -- and javac is fairly large
and gnarly.
* Doing most things involving more than just compilation syntax or
simple changes/additions to core Java classes is rather daunting
in OpenJDK. There were large portions of some presentations at
JavaOne outlining just how hard this is when one has to consider
native and Java code and their memory interactions with GC, etc.
Also, from everything I've heard, OpenJDK is still a rather gnarly
codebase. Being able to open a top-level project in an [ideally
free] IDE on each platform, simply hit "build" and get the same
result as Sun, and have full code completion / navigation data
would be a really helpful starting point... Project Maxine really
struck me as compelling way out of many of these issues -- but it
is in its research infancy and could have been killed for all I
know (I never heard it mentioned by Sun folk at this year's
JavaOne...).
* Neil Gafter certainly availed himself of javac, OpenJDK, etc, and
produced a BGGA prototype. After all of this work, it went
nowhere. Various Sun folk said they simply had no resources to
properly deal with the proposal. This has to make others gunshy
of investing their time and effort.
* There is also a sense that any such effort won't bear fruit for
years -- as JDK development cycles are pretty long, JDK feature
freezes come pretty early, and at least some of us can't actually
/use /any feature until it is available on /all /of our platforms
in a normal released JDK. In my case, this platform mix includes
AIX, which automatically adds at least a year and usually more
beyond Sun's development cycle. [Yes, this is beyond Sun's
control and one of my major gripes with IBM -- that and their lack
of consistency with Sun's JVM implementation.]
* I /desperately /want a "controlled" form of multiple inheritance
in Java ala traits or mixins. The reduction in clumsy hand wiring
to various delegate objects is clear to anyone who has used such
features. Java has always been extremely clumsy in this regard
and this has been clearly evident from day one. This needs to be
fixed! Just because Sun said no to C++'s complex, problematic,
uncontrolled and chaotic multiple inheritance does not mean Java
should throw out the baby with the bathwater! In this case Sun
has repeatedly told me and others "no", with no good reason other
than a dogmatic "multiple inheritance is bad and will never be in
Java". This is madness. Simply allowing something like:
public interface MyTrait
{
public Foo getFoo();
public void operateOnFoo()
{
// default implementation calling getFoo() as needed
}
}
would be huge -- and only requires that interfaces be allowed to
provide implementation [and something like MyTrait.operateOnFoo() in
cases where there is ambiguity between implementations]. One could
also introduce a new contextual keyword of "trait" rather than
"interface" here for clarity, but that seems unnecessary.
Finally, we did discover the ability to auto-generate base classes via
annotation processors. It's not immediately clear that this is possible
from perusing the documentation, but this approach does open up a lot of
doors...
--
Jess Holle
jddarcy wrote:
> After listening to episode 277, I'm led to conclude I'm thought of by
> some as one of the "ivory tower guys" who "just says no" to ideas
> about changing the Java programming language.
>
> I have a rather different perspective.
>
> In November 2006, Sun published javac and related code under the
> familiar GPLv2 with Classpath exception. [1]
>
> Shortly thereafter in January 2007, no less a Java luminary than James
> Gosling endorsed the Kitchen Sink Language (KSL) project. [2] In
> James' words KSL is "A place where people could throw language
> features, no matter how absurd, just so that folks could play around"
> since he has "... never been real happy with debates about language
> features, I'd much rather implement them and try them out."
>
> KSL received no significant community response.
>
> Later in 2007, after the remaining core components of the platform
> were published as open source software as part of OpenJDK during
> JavaOne, in November Kijaro was created. [4] Kijaro is similar in
> spirit to KSL, but not does require contributors to sign the Sun
> Contributor Agreement (SCA). Before Project Coin, Kijaro saw a modest
> number of features developed, fewer than ten, which is also not a
> particular vigorous community response given the millions of Java
> developers in the world.
>
> The earliest posts on what would become Project Coin mentioned the
> utility of prototypes, the Project Coin proposal form included a
> section to provide a link to an optional prototype, and I repeated
> stated throughout Project Coin the helpfulness of providing a
> prototype along with a proposal.
>
> Despite the availability of the OpenJDK sources for javac and the
> repeated suggestions to produce prototypes, only a handful of
> prototypes were developed for the 70 proposals sent into Project Coin.
>
> Dick asked rhetorically during the podcast whether alternative
> projects exploring language changes were inevitable as the "only
> approach given strict control exercised over the JVM [by Sun]."
>
> IMO, such approaches are inevitable only if Sun's repeated efforts to
> collaborate continue to be ignored.
>
> Classes on compilers are a core component of many undergraduate
> compiler science curricula. All the Java sources in the JDK 7
> langtools repository adds up to about 160,000 lines of code and javac
> itself is a bit over 70,000 lines currently. These are far from
> trivial code bases and some portions of them are quite tricky, but
> implementing certain changes isn't that hard. Really. Try it out.
>
> Dick says toward the end of the opening segment "If people do want to
> do this stuff, right now they are being told they can't."
>
> I certainly do not have the authority to tell others what they can and
> cannot do. Indeed, I have advocated producing prototypes of language
> changes as a much more productive outlet than whining and pouting that
> other people aren't busy implementing the language changes you want to
> little avail. Others have already noted in previous messages to this
> group the irony of Lombok using the annotation processing facility I
> added to javac in JDK 6 as an alternate way to explore language
> changes (together with an agent API to rewrite javac internal
> classes!) . However, way back before JDK *5* shipped in 2005, we at
> Sun recognized that annotation processors by themselves would be a
> possible way to implement certain kinds of de facto language changes.
> The apt tool and later javac were always designed to be general meta-
> programming frameworks not directly tied to annotations; for example,
> an annotation processor can process a type containing no annotations
> to, say, enforce a chosen extra-linguistic check based on the
> structure of the program.
>
> As an example of what can be done just using annotation processing,
> long-time annotation processing hacker Bruce Chapman implemented
> "multi-line strings" as part of his rapt project [5]; the value of the
> string is populated from a multi-line comment. After repeatedly
> outlining how it would be possible to do so on the annotation
> processing forum [6], I've gotten around to hacking up a little proof-
> of-concept annotation processor based implementation of Properties.
> [7] The user writes code like
>
> public class TestProperty extends TestPropertyParent {
> protected TestProperty() {};
>
> @ProofOfConceptProperty
> protected int property1;
>
> @ProofOfConceptProperty(readOnly = false)
> protected long property2;
>
> @ProofOfConceptProperty
> protected double property3;
>
> public static TestProperty newInstance(int property1,
> long property2,
> double property3) {
> return new TestPropertyChild(property1, property2, property3);
> }
> }
>
> and the annotation processor generates the superclass and subclass to
> implement the desired semantics, including the getter and setter
> methods, etc. Using annotation processors in this way is a bit clunky
> compared to native language support, but if people want to experiment,
> the capabilities have been standardized as part of the platform since
> JDK 6.
>
> It is technically possible to take the OpenJDK sources and construct a
> version of javac that accepts language extensions; after all, this is
> how we generally evolve the language and also how the JSR 308 changes
> were developed before going back into the JDK 7 code base.
> Additionally, the IcedTea project and the shipping of OpenJDK 6 in
> Linux distributions has provided an existence proof that folks other
> than Sun can take the entire OpenJDK code base, add various patches
> and additional components to it, and ship it as a product.
>
> Given the OpenJDK sources Sun has published, subject to the license
> and trademark terms and conditions, anyone is free to implement and
> use language changes, *as long as* they assume the costs and
> responsibilities for doing so. Experimentation has long been
> encouraged and experiences from experiments using language changes on
> real code bases would certainly better inform language evolution
> decisions. Unfortunately, others have generally not done these
> experiments, or if the experiments have been done, the results have
> not be shared.
>
> I also do not have the power to prevent others from using non-Java
> languages on the JVM or to force others to run anything on the JVM,
> nor would I want to exercise such powers even if I had them. Indeed,
> for some time Sun has endorsed having additional languages for the
> platform and the main beneficiary of John Rose's JSR 292 work will not
> be the Java language, but all the non-Java languages hosted on top of
> the JVM.
>
> I do have the authority to speak on what Sun will and will not spend
> our resources on in relation to Project Coin, certainly a right any
> organization reserves to do with its resources.
>
> If there are frustrations waiting for Java language changes, I assure
> you there are also frustrations working on Java language changes. For
> example, I find it frustrating (and self-inconsistent) that people
> state "I don't have technical expertise in this area" while
> simultaneously expecting their preferences to be selected without any
> contribution on their part. [8]
>
> Finally, going back to a white paper from 1996, the design of Java
> quite intentionally said "No!" to various widely-used features from
> the C/C++ world including a preprocessor and multiple inheritance.
> Again since the beginning, Java admittedly borrowed features from many
> other established languages. [9] Given the vast number of potential
> ways to change the language that have been proposed, many language
> changes will continue to be called and few will continue to be
> chosen. In any endeavor there is a tension to balance stability and
> progress. For the Java language, given the vast numbers of
> programmers and existing code bases, we try to err on the side of
> being conservative (saying "No." by default) first to do no harm, but
> also to preserve the value of existing Java sources, class files, and
> programmer skills.
>
> There are many other fine languages which run on the JVM platform and
> I expect the Java language to continue to adopt changes, big and
> small, informed both by direct experiments with prototypes and by
> experiences with other languages.
>
> -Joe Darcy
> Project Coin Lead
>
> [1] http://blogs.sun.com/ahe/entry/javac_open_sourced
>
> [2] https://ksl.dev.java.net/
>
> [3] http://blogs.sun.com/jag/entry/compiler_fun
>
> [4] https://kijaro.dev.java.net
>
> [5] https://rapt.dev.java.net/; see also Bruce's https://hickory.dev.java.net/
>
> [6] http://forums.sun.com/forum.jspa?forumID=514
>
> [7] http://blogs.sun.com/darcy/entry/properties_via_annotation_processing
>
> [8] http://blogs.sun.com/darcy/entry/project_coin_final_five#comments
>
> [9] http://java.sun.com/docs/white/langenv
>
> >
>
>
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