(tl;dr Packages can now declare themselves as modules instead of simple namespaces, and they get to choose exactly what they export and what other modules they require. Projects can now resolve their types from within modules with a module path instead of on a per-type basis from the class path. It's a huge step forward for Java modularity and dependency management.)
I have a hard time being too impressed because more modern languages are doing this out of the gates and with far fewer hacks and more out-of-the-box tooling (e.g. Rust), but acknowledge just how monumental of an effort it was to design the new system and then build it into Java's core in a way that's mostly backwards-compatible. Java's going to be around for a long time, and this is a big long-term gain for the ecosystem.
I'd really love to see languages like Ruby tackle this next. It's sorely needed.
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Haha...I love Rust, but you must not have been following the recent saga over modules in the community. Two things became abundantly clear:
1) There are definite issues with the current way that Rust does modules and they create problems for newcomers that don't know all the intricacies.
2) There's very little consensus in the community about the best way to fix those problems.
Initially, a couple of different, somewhat major proposals were made that would largely overhaul the system. Over the course of a few iterations, those were whittled down to a few, much smaller changes that mostly keep the current system but remove some of the stumbling blocks. It's a credit to the Rust team that they've handled it in such an open manner, but it's also creating a bit of a "design by committee" feel that's probably going to create something that everyone can live with and very few will think is close to perfect.
FWIW, I don't agree with the "design by committee" assessment on the new system, either. There was certainly a lot of committee-flavored input, but it was only used for brainstorming and gathering requirements. The actual RFC, especially at this point, is pretty coherent and put together by only one or two people.
I wish that the term "design by committee" didn't have the stopping power it has. Rust's current module system absolutely wasn't designed by committee, and if there's one complaint that I'd levy against it it'd be "overengineered", which is typically what people seem to tend to expect from systems designed by committees!
Personally, whether or not something is designed by a committee is orthogonal. What matters more is whether that something is well-integrated with the sibling systems that it is integrated with (read: unsurprising), and whether its design exhibits good taste (obviously, openly, wantonly subjective, but perhaps we can usefully say that a design can be judged to have good taste if it is so judged by people who think that its sibling systems also have good taste (so read: consistent)).
In truth, there probably is a positive correlation between things that are designed by committee and things that violate the two principles above; it's hard to get lots of people to commit to a consistent vision, especially if that involves serious tradeoffs. It's part of why languages with BDFLs tend to be considered at least coherent, if not elegant: it's easy for a committee of one to have a vision consistent with itself. But where this pejorative doesn't necessarily apply is when the committee is small, close-knit, and all share the same values.
When it comes to Rust, the committee in question is the language team, which is just seven people (in contrast to the dozens of commenters on this issue, who are there to provide perspective and arguments, not to cast votes). Of these, the team lead (Niko Matsakis) is someone that I personally trust to have excellent taste; I feel the same about the RFC author, Aaron Turon, who is also on the language team. And, for better or worse, teams choose their own new members, which gives good taste the chance to propagate; this runs the risk of stagnation (lessened, hopefully, by the RFC process), but also avoids the fractured nature of committees assembled from far afield.
For the record, the module system is exactly one of those things that I've long felt is subpar about Rust (though still better than headers, obviously--that's not a debate, it's a massacre). I haven't had the chance to play with the revised modules RFC yet, but we'll have a lot of experience with it before it potentially gets stabilized, and from what I've read it does look like it ultimately improves consistency and reduces surprises when judged against the rest of the language, which makes me optimistic. I'd love to have to find something new about Rust to whine about. :)
The problem with Java is that it's an already established and very popular platform and it's been so for the past decade at least. When starting from scratch, it's easy to just throw it all away and start fresh, it's easy to fix mistakes that were made in the past.
The irony though is that we still have a hard time learning from history. Just look at Go. Sometimes this industry feels like Groundhog Day, the movie.
Also, no platform or language that I know of has gotten "modules" right, with Java being one of the platforms that has gotten closest to fixing the problem actually (by means of OSGi). To see why modules are still a big problem and why we won't have a fix for the foreseeable future, I invite you to watch this keynote by Rich Hickey: https://www.youtube.com/watch?v=oyLBGkS5ICk
Well of course - it's easier to build something like this into a clean-slate language isn't it? It's harder to build it into an existing language and VM spec with an incomprehensibly large volume of existing code to be compatible with. It's backwards to say it's not impressive because someone else with zero constraints to work with also managed it.
I hope my original comment was relatively clear on this, but sure, it's a big accomplishment and will be a quantum leap for the ecosystem. However, given that languages elsewhere have had better systems for quite some time now, it's not like they're advancing the state of the art in dependency management.
But again, it wasn't an easy thing to do (a very hard thing even) and everyone involved deserves major felicitation.
A module system in and of itself is not impressive these days. Getting one into Java is.
I'm not so sure about that. Java (both the language and the VM) is relatively unique in its mix of static (mostly in the sense of being typed) and dynamic (all linking is dynamic; code is often be loaded, unloaded and generated at runtime; reflection and general introspection of the runtime is pervasive). It's a blend of, say, ML, Smalltalk and Erlang. The module system is therefore more impressive than it may look at first glance. While not all the tooling is there yet, through the use of what it calls "layers", it makes it possible to dynamically load plugins or even upgrades to components in the system, each depending on different versions of the same library, while enforcing customizable levels of isolation between them. Whether or not there are any conflicts requiring a separation of "layers", can also be determined at runtime by introspection.
(0) A unit of encapsulation: Modules can export abstract types whose representation is hidden from the rest of the program.
(1) A unit of type-checking: Modules can be type-checked without knowing anything other than the interface of their dependencies.
(2) A unit of translation: Modules can be translated to target machine code separately from each other. (That being said, whole-program compilation is fine if you want it. The semantics of the module system shouldn't make it mandatory, though.)
Most programming languages don't have module systems at all. And most programming languages that do have module systems, have module systems that suck. Including Rust.
I'm curious, is there another language that allows you to streamline its runtime by choosing only what modules your app needs?
Other than that, the majority of compiled languages do remove unused library code when static linking.
Could you expand on that? Why Ruby?
What jigsaw and rust call modules are isolated components that you can plug and connect in various configurations, and that declare public interfaces both as dependencies and as exported symbols. Consider a module configuration like
module java.sql {
requires public java.logging;
requires public java.xml;
exports java.sql;
exports javax.sql;
exports javax.transaction.xa;
}
Also, by default ruby does not namespace things by package/module/gem so it's easy to have collisions, while in a more robust system this would/should be under the control of the calling code.
One thing I will say though is Java 9 has had a definite improvement on Java applications that run on my Raspberry Pi 3, I think because this got included http://openjdk.java.net/jeps/297
One application used to take 55s to start up, now it takes around 15s!
Still sounds ridiculous. Assuming this is how much time it takes to initialize the VM, I wonder if it would be possible to have a pool of VM processes that are already running and ready to accept an application code.
This was tried with Drip and the earlier Nailgun. The idea doesn't work as well as you'd think for several practical reasons (the JVM is very lazy, so a JVM that does nothing until it has user code to run does just that - nothing).
Why would you assume that?
So from now on the OpenJDK will be as fast as Oracle VM on ARM!
Also why are you even considering go as modern? The best compiled alternative to java is D and it's possible to disable the stop the world pause for specific threads by detaching them from the runtime which make it useful for realtime workloads while still being able to take advantage of the GC to boost your productivity when determinism is not important.
Anyhow, I think this is a great step forward for Java.
Is there anywhere the design goals and constraints for modules are? I'd really like to know how they ended up in their current form.
That was only a few weeks. If you check the official release schedule http://openjdk.java.net/projects/jdk9/ Jigsaw was supposed to be feature complete a year before that vote happened. Jigsaw was simply not close to ready when it was merged to master. And yes, Oracle still claims it hit every milestone on that schedule.
> It was changed and revoted upon, but it's hard to follow what was modified to make it acceptable.
http://openjdk.java.net/projects/jigsaw/spec/minutes/2017-05...
http://openjdk.java.net/projects/jigsaw/spec/minutes/2017-05...
http://openjdk.java.net/projects/jigsaw/spec/minutes/2017-05...
Not much really. Basically Oracle called their bluff. At that point is was really too late as Jigsaw was already merged to master and more or less touched every part of the JDK.
> Is there anywhere the design goals and constraints for modules are? I'd really like to know how they ended up in their current form.
Not really, it was really just Oracle making things up as they went. For the past ten years Mark Reinhold would give talks at Java conferences what the module system comping in the next Java version was supposed to do and every year the content was different. For example they have no good explanation while they mashed the module declaration into a .class file, basically everybody except Oracle thinks it's a bad idea but the just went with it anyway. They claim "reliable configuration" as a goal but without versioning that's meaningless.
Versioning is not currently built into Jigsaw, but Jigsaw provides all the building blocks necessary to support it in third-party tools.
> For the past ten years Mark Reinhold would give talks at Java conferences what the module system comping in the next Java version was supposed to do and every year the content was different.
Plus the entire development was done in the open, in an open source project with an active mailing list and frequent prototypes.
Edit: To add to my question, jar hell was solved by tooling which generates your classpath for you. So it hasn't been an issue for me in years. And they refused to add versioning, so you still need to use those tools. Strong encapsulation just means they disabled reflection access to non public members, which I consider a regression on functionality. Either way, not a particularly useful feature to me, in fact it breaks some of my code. So I'm left with being able to have small JVMs which don't bundle the full standard lib, which seems to be mostly of use for memory constrained environments like IOT. But I'm actually hopeful there's some bigger practical benefits I'm not thinking of, so I'd love to hear from people who know more about jigsaw.
Before Java 9, the only way to hide private APIs would be to have everything in the same JAR.
If a library is splinted across multiple JARs, then private APIs only to be used internally by library become exposed to everyone, and there will always exist someone making use of them even if explicitly marked as internal.
This is nothing new to Java, other languages e.g. Ada, Delphi, .NET and even Go have this kind of visibility concept.
Good news regarding any trepidation on the differencesa between the runtimes — recently we announced that there will no longer be a difference between OpenJDK and OracleJDK [1]
To quote: “The Oracle JDK will primarily be for commercial and support customers once OpenJDK binaries are interchangeable with the Oracle JDK (target late 2018)”
[1] https://blogs.oracle.com/java-platform-group/faster-and-easi...
When Jigsaw was delayed I was playing with the idea to create a project called shitty-jigsaw, which would just merge all of the packages in a module and change the access modifiers to be more restrictive according to some module definition.
I remember it was released at some point, but at the end it didn't amount to much since most of the JVM's actual implementation relied on everything else and the "optional" bits were only a small part, so it didn't help almost at all with applets. And by that time Java applet gaming was dead (it never reached Flash gaming's heights, but for a few years in the early/mid 2000s it was still something you could make a living off - if you didn't expect much).
I never heard about it much after that and personally moved away from Java with Flash becoming dominant on the web game scene and soon with Oracle being an dick to everyone. The only reason i used Java was for NetBeans' GUI editor for my tools but with Lazarus [0] becoming very stable by that time and NetBeans looking and behaving weird in my -then- brand new iMac, i abandoned Java for good (the only active Java project i still have is a tilemap editor [1] but this only if you stretch "active" to "hack on it a little every few years").
I also never liked Java much after Java 1.4 - it moved further away from its "simple language" roots and i liked how everything was solved in the library instead of adding extra stuff to the language. Well, that, and things like generics felt very "bolted on" while annotations like `@override` felt unnecessary verbosity (and ugly syntax-wise).
My favorite Java was probably around 1.1 or so (i have a book on that too), some times i think i should make a new language and VM after it but i lose interest quickly - i think i have a bunch of parsers for Java-1.1-like languages lying around in my backups, from every time i get that urge :-P.
[0] http://www.lazarus-ide.org/ [1] http://runtimeterror.com/rep/mapas
http://www.oracle.com/technetwork/java/javase/kernel-135055....