> On 30 Jan 2026, at 19:58, Steffen Yount <[email protected]> wrote: > > Hi Ron, > > The problem I encounter—every time there is a planning meeting for a > new service deployment—is the increasing preference for non-Java > toolchains like Rust, Go, and even TypeScript.
Note that, with the possible exception of TypeScript, the languages you mentioned are far less popular than Java today, and show no sign of closing the gap. I’m certainly not saying they should be ignored, and we obviously keep abreast of developments in the programming language space, but adopting a feature cannot be justfied *just* because a far less successful language has it. > > The acute ceremony I described with ServiceLoader is merely a symptom. Okay, but since that is the symptom you’ve chosen to focus on, can you please describe it? Maybe it can be addressed on its own, and maybe as part of a larger change that can cure multiple symptoms, but first we need to know what it is. The reason saying “ceremony” isn’t enough is this: Suppose some operation in Java takes 20 lines instead of 2. If this operation is done once every 10K lines, then this 10x improvement would amount to a 0.2% benefit, while still incurring the cost of complicating the language. Such a vague description simply isn’t actionable, and to improve things we need actionable information. > It remains a library-level escape hatch for a problem—polymorphic > static dispatch and retroactive extension—that the language currently > cannot express natively. Instead of talking in the abstract about a missing mechanism, can you please detail the specific problem you’ve encountered and are suggesting we should solve, in a way that will allow us to determine how serious of a problem this is compared to other problems we need to solve? > Without these facilities, Java remains > "corralled" in an instance-based model while the industry moves toward > the zero-cost, static-binding models of our competitors. I don’t know what “an instance-based model” is and Java’s ability to make some operations zero-cost matches or exceeds most of our competitors already. Obviously, there’s plenty of room for improvement, but talking in such an abstract way doesn’t help us improve anything. If you want to help us improve Java, show us the code you have to write today, and explain why it’s problematic and why it’s an important problem to prioritise. As Brian Goetz says, “tell us something we don’t know”. We know what features TypeScript and Go and Zig and Julia and Elixir and Rust and ATS and Python and C++ and Nim have. We don’t know what problem *you* ran into and believe is serious enough for the platform to solve. — Ron > > > On Wed, Jan 28, 2026 at 4:31 PM Ron Pressler <[email protected]> wrote: >> >> The first two paragraphs boil down to “it’s difficult to work with >> user-defined numeric types, especially with a tight memory layout”. As you >> probably know, this is a problem we’re already working on solving. >> >> Aside from that, I think the problem you’re reporting is: >> >> "The java.util.ServiceLoader ... requires explicit custom code to verify >> bindings at startup for fail-fast behavior. The API remains an extra >> invocation hurdle with its lookup and instantiation requirements.” >> >> What you’re saying about “right-sizing” the language is absolutely right, >> but for the JDK team to propose a solution to a problem you’ve identified, >> the problem first needs to be understood. Assuming that what I quoted is the >> problem you’ve tried expressing, can you elaborate more on: >> >> 1. Requires explicit custom code to verify bindings at startup for fail-fast >> behavior. >> >> 2. The API remains an extra invocation hurdle with its lookup and >> instantiation requirements. >> >> The more concrete you are, as in “I tried to do X and this is the code I >> wrote”, the easier it would be to understand. >> I think I know what you mean in #1, but it would be helpful to show what >> code you had to write. In #2, what is exactly the hurdle? E.g. let’s say >> that the hurdle is that the API is verbose. That is only a problem if it has >> to be used lots of times in a program, so what was your program that >> required so many uses of ServiceLoader? >> >> (P.S. “right-sizing” the language doesn’t mean that anything that could be >> improved with a language feature should be because every addition to the >> language complicates it. We like it when a non-trivial language feature can >> solve a big problem or multiple small ones.) >> >> — Ron >> >> >>> On 28 Jan 2026, at 23:20, Steffen Yount <[email protected]> wrote: >>> >>> Hi Ron, >>> >>> Thank you for the feedback. It's totally reasonable to push for the >>> "why" before getting into the "how." >>> >>> The personal problem I encounter is the severe and inconvenient >>> extensibility costs of the current language model. When pursuing >>> data-oriented design or domain-specific numeric types in Java, I find >>> the language's current facilities to be a significant design obstacle. >>> These are not just issues I find while building, but constraints that >>> fundamentally alter how I consider a project's architecture before a >>> single line of code is written. >>> >>> I have encountered the following specific friction points: >>> >>> The Instantiation Tax: On several occasions, I have turned to Java for >>> intensive math calculations. These efforts typically start small but >>> eventually outgrow Java's supported numeric abstractions. To move >>> beyond small memory footprints and 64-bit representational limits, I >>> find I must refactor to contiguous arrays, reusable Flyweight objects, >>> and custom math methods just to manage the memory pressure and data >>> type limitations. Because I cannot define polymorphic static contracts >>> for these types, I am forced to pay an Instantiation Tax—maintaining >>> "witness" objects just to access static logic. The ergonomic noise and >>> heap-inefficiency of the unwanted object headers are so high that I am >>> often discouraged from pursuing my original abstractions entirely. >>> While I have used primitive long types as witnesses for static >>> overloaded method binding, using the NewType pattern for type-safe >>> bindings remains prohibitively expensive; a new NewType class's >>> implementation immediately excludes it from participation within the >>> language's built-in expression operators. In the aforementioned >>> efforts, I have ultimately abandoned Java for C/C++ simply because >>> they allowed me to shape the data layout and its static behavior >>> without this "abstraction tax." >>> >>> The Expression Problem (Post-hoc Abstraction): When I find it >>> necessary to treat third-party classes as part of a common >>> abstraction—for instance, when attempting to resolve Guice-based >>> injection or AOP design issues without the "magic" of runtime >>> reflection—the traditional path is the Adapter Pattern. I find this >>> route unsustainable; creating a new wrapper class for every instance >>> not only fragments object identity but generates significant GC churn. >>> I have seen production code with wrapper classes nested eight levels >>> deep just to satisfy disparate abstractions. The ability to implement >>> type level contracts rather than just instance level contracts, along >>> with type level extension methods, would allow us to side-step the >>> wrapper classes with implementations that bind to existing types >>> without modifying their source code. The lack of them serves as a wall >>> preventing me from designing the clean, type-safe, and AOT-friendly >>> systems I know are possible elsewhere. >>> >>> The ServiceLoader Ceremony: The java.util.ServiceLoader acts like more >>> of a library than a language feature. It requires explicit custom code >>> to verify bindings at startup for fail-fast behavior. The API remains >>> an extra invocation hurdle with its lookup and instantiation >>> requirements. A coherent language-integrated, static service interface >>> method dispatch and binding would dramatically reduce this ceremony >>> and increase utility by moving it from a manual runtime search to a >>> link-time certainty. >>> >>> My "big picture" problem is that Java’s evolution model currently >>> makes it difficult to "grow the language" via libraries that feel >>> native and are performan, such as the recent prototype exploration of >>> Float16. I believe the language should provide the infrastructure for >>> _Static Service Traits_ or otherwise make that kind of library-driven >>> growth a standard capability for all developers. >>> >>> I feel "corralled" into 1990s instance-based OOP. When I explore >>> data-oriented design or high-performance numeric abstractions, the >>> features found in my competitors' language tool belts would be >>> incredibly useful; without them, I find myself looking at alternate >>> language implementations just to avoid Java's structural obstacles. >>> >>> Given that Project Amber’s stated mission is to "right-size language >>> ceremony" and improve developer productivity, doesn't a proposal that >>> eliminates this Instantiation Tax and link-time service ceremony seem >>> like a relevant and worthy pursuit? >>> >>> -Steffen >>> >>> >>> On Wed, Jan 28, 2026 at 7:45 AM Ron Pressler <[email protected]> >>> wrote: >>>> >>>> The hardest part in designing and evolving a language is deciding which >>>> problems are important enough to merit a solution in the language and how >>>> their priorities compares to other problems. It’s the hardest part because >>>> the language team are expert at coming up with solutions, but they may not >>>> always know what problems people enoucnter in the field, how frequently >>>> they encounter them, and how they work around them today. >>>> >>>> I’m sure there is some problem hidden here and in your previous post, but >>>> it is not articulated well and is hidden in a poposed solution, even >>>> though no solution is even worth exploring before understanding the >>>> problem. And so the best way to get to a solution is for you to focus on >>>> the problem and only on the problem. >>>> >>>> What was the problem you *personally* ran into? How bad were its >>>> implications? How did you work around it? >>>> >>>> With the hard part done, the JDK team will then be able to assess its >>>> severity and think whether it merits a solution in the JDK, if so, where >>>> (language, libraries, or VM), and how to prioritise it against other >>>> problems worth tackling. Then they’ll be able to propose a solution, and >>>> that’s would be the time to try it out and discuss it. >>>> >>>> — Ron >>>> >>>> >>>> >>>>> On 28 Jan 2026, at 00:28, Steffen Yount <[email protected]> wrote: >>>>> >>>>> The recent thread "Java Language Enhancement: Disallow access to static >>>>> members via object references" highlights a long-standing tension in >>>>> Java's handling of static members. While that thread seeks to further >>>>> decouple instance state from static logic, I would like to propose moving >>>>> in the opposite direction: "doubling down" on Java’s compile-time and >>>>> link-time static polymorphism. >>>>> >>>>> By beefing up java.util.ServiceLoader facilities and integrating its >>>>> discovery mechanism directly into the language via Static Service Traits, >>>>> we can facilitate the "Witness Object" paradigm discussed by Brian >>>>> Goetz's "growing the java language" presentation and the algebraic >>>>> "well-known interface" model for custom numeric types (like Float16) >>>>> proposed in Joe Darcy's "Paths to Support Additional Numeric Types on >>>>> the Java Platform" presentation. >>>>> >>>>> == Static Service Traits for Java == >>>>> >>>>> I propose a system of Static Service Traits. I use the term "Trait" >>>>> advisedly: this feature adopts a rigorous Coherence Model (inspired by >>>>> systems like Rust) to ensure that service resolution is not merely a >>>>> dynamic search, but a type-safe, deterministic binding of static >>>>> capabilities to types. >>>>> 1. The service Contextual Keyword >>>>> We introduce service as a contextual modifier for interface declarations. >>>>> Marking an interface as a service identifies it as a "service type" with >>>>> a contract for static capabilities and a high-performance service >>>>> provider registry. >>>>> >>>>> 2. Static Implementations and Extension Methods >>>>> • Static Implementations: >>>>> • In Interface Headers: interface MyTrait implements ServiceX<T>. >>>>> Methods are fulfilled as static. >>>>> • In Class Headers: class MyClass implements static >>>>> Numeric<Float16>. Methods are implemented as static on the class. >>>>> Existing signature rules prevent a method from being both a static and an >>>>> instance implementation simultaneously. >>>>> • Static Extension Methods: Desugared at the call site. >>>>> myInstance.method() becomes MyClass.method(myInstance). Notably, if >>>>> myInstance is null, it desugars to MyClass.method(null) without an >>>>> immediate NullPointerException. >>>>> • Ergonomic Aliases: To simplify signatures, we introduce private >>>>> nested static type aliases This and Super (e.g., static This add(This a, >>>>> This b)). >>>>> >>>>> 3. Operational Mechanics & Link-Time Integration >>>>> A ServiceLoader Controller is integrated into the JVM’s class-loading >>>>> pipeline. During class definition, the Controller eagerly extracts all >>>>> relevant metadata to populate the Static Service Provider Registry, >>>>> including: >>>>> • Header-level static implements and implements declarations. >>>>> • Service binding descriptors from module-info.class. >>>>> • META-INF/services/ provider-configuration files. >>>>> Hierarchical Precedence Resolution: To ensure deterministic binding, the >>>>> Controller resolves call sites to their most specific service provider >>>>> via a waterfall dispatch model: >>>>> • Tier 1: Type Specialization: Most specific generic match wins, >>>>> applying the same scrutiny and rules currently used for existing static >>>>> overloaded method resolution. >>>>> • Tier 2: Physical Locality: Provider in the same file (.jar/.class) as >>>>> the caller wins. >>>>> • Tier 3: Loader Proximity: Nearest ClassLoader in the delegation path >>>>> wins. >>>>> • Tier 4: Modular Topology: Internal > Explicit > java.base > >>>>> Transitive > Automatic. >>>>> • Tier 5: Sequential Order: Final tie-breaker via Classpath order. >>>>> >>>>> 4. Coherence, The Orphan Rule, and Quarantining >>>>> To achieve the type-safety of a trait system, we enforce an adapted >>>>> Orphan Rule: A module (or package on the classpath) must own either the >>>>> service interface or the target type to define an implementation. >>>>> • Coherence Enforcement: Violations in modular code trigger a >>>>> LinkageError. >>>>> • Behavioral Continuity: Violations in classpath code trigger a >>>>> load-time warning and the provider is quarantined from the Static >>>>> Registry. To ensure continuity, quarantined providers remain accessible >>>>> via existing java.util.ServiceLoader API calls, protecting legacy >>>>> iteration-based discovery while ensuring the integrity of the new >>>>> link-time dispatch. >>>>> 5. Performance and AOT Considerations >>>>> This model transforms ServiceLoader into a link-time resolver. JIT >>>>> compilers can treat service calls as direct invokestatic instructions, >>>>> enabling aggressive optimization. This is highly compatible with Project >>>>> Leyden and GraalVM, as precedence can be "baked" into the binary during >>>>> AOT compilation. >>>>> Conclusion >>>>> By transitioning ServiceLoader to a link-time resolver, we provide a >>>>> type-safe, high-performance path for algebraic types and witness-based >>>>> generics. This allows Java to "grow" through libraries—fulfilling the >>>>> goals of both Darcy and Goetz—while maintaining the performance and >>>>> stability characteristics of the modern JVM. >>>>> >>>>> >>>>> Thoughts? >>>> >>
