JDK 19: The brand new options in Java 19

Java Improvement Equipment 19, due this September, has simply had a seventh function proposed for it: structured concurrency, to simplify multithreaded programming. Structured concurrency joins six earlier options together with report patterns, a preview of a international operate and reminiscence API, and help for the open supply Linux/RISC-V instruction set structure (ISA).

JDK 19, or just Java 19, probably may host an unlimited variety of options, starting from common generics to worth objects, based on plans underway for enhancing Java. JDK 19 would comply with JDK 18, which arrived March 22. Customary Java is on a six-month launch cadence.

OpenJDK’s builders have printed an official launch schedule for JDK 19, which has it arriving September 20 as a manufacturing launch, preceded by rampdown phases June 9 and July 21, and launch candidates to be printed August 11 and August 25.

Early entry builds of JDK 19 may be accessed from jdk.java.internet/19. Proposed JDK 19 options embody:

• Structured concurrency, in an incubator part, is meant to simplify multithreaded programming by means of a structured concurrency library. This concurrency treats a number of duties operating in several threads as a single unit of labor, to streamline error dealing with and cancellation. Reliability and observability are improved.
• A preview of report patterns, to deconstruct report values. Document patterns and sort patterns may be nested to allow a declarative, highly effective, and composable type of information navigation and processing. Objectives of the proposal embody extending sample matching to specific extra subtle, composable information queries whereas not altering the syntax or semantics of sort patterns. This proposal builds on sample matching for instanceof, delivered in JDK 16  in March 2021. Future plans might name for report patterns to be prolonged with capabilities similar to array patterns and vararg patterns. Document patterns is a part of Mission Amber, an effort to discover and incubate smaller, productivity-oriented Java options.
• A preview of a international operate and reminiscence API, which might introduce an API by which Java applications can interoperate with code and information outdoors the Java runtime. By effectively invoking international features (i.e., code outdoors the Java runtime) and safely accessing international reminiscence (i.e., reminiscence not managed by the JVM) the API permits Java applications to name native libraries and course of native information with out the hazard and brittleness of the Java Native Interface (JNI). The international operate and reminiscence API combines two earlier incubating APIs: the international reminiscence entry API and the international linker API. The international operate and reminiscence API was beforehand incubated in JDK 17 and reincubated in JDK 18. The proposal’s targets embody ease of use, efficiency, generality, and security.
• A preview of digital threads, that are light-weight threads that dramatically scale back the hassle of writing, sustaining, and observing high-throughput, concurrent functions. Objectives embody enabling server functions written within the easy thread-per-request model to scale with near-optimal {hardware} utilization, enabling current code that makes use of the java.lang Thread API to undertake digital threads with minimal change, and allow troubleshooting, debugging, and profiling of digital threads with current JDK instruments. It isn’t a aim of this proposal to alter the fundamental concurrency mannequin in Java or supply a brand new information parallelism assemble in both the Java language or Java libraries. Neither is it a aim to take away the normal implementation of threads or to silently migrate current functions to make use of digital threads.
• A 3rd preview of sample matching for change expressions and statements, extending sample matching to change, to permit an expression to be examined towards plenty of patterns, every with a selected motion, so advanced data-oriented queries may be expressed concisely and safely. This functionality beforehand was previewed in JDK 17 and JDK 18. The third preview would add refinements together with the alternative of guarded patterns with when clauses in change blocks. Additionally, the runtime semantics of a sample change when the worth of the selector expression is null are extra intently aligned with legacy change semantics. The plan’s targets embody increasing the expressiveness and applicability of change expressions and statements by permitting patterns to seem in case labels. Different targets embody permitting builders to calm down the historic null-hostility of change when desired, growing the security of change statements and guaranteeing that current change expressions and statements proceed to compile with no modifications and execute with an identical semantics.
• A fourth incubation of a vector API that will specific vector computations that reliably compile at runtime to optimum vector directions on supported CPU architectures, thus reaching efficiency superior to equal scalar computations. Builders utilizing the API acquire a approach to write advanced vector algorithms in Java, utilizing the HotSpot auto-vectorizer however with a person mannequin that makes vectorizations extra predictable and strong. The vector API beforehand was incubated into JDK 16, JDK 17, and JDK 19.
  Enhancements to the API proposed for JDK 19 embody enhancements to load and retailer vectors to and from MemorySegments, as outlined by the Overseas Operate and Reminiscence API preview. JDK 19 would additionally add two cross-lane vector operations, compress and develop, along with a complementary vector masks compress operation. The compress vector operation maps lanes of a supply vector, chosen by a masks, to a vacation spot vector in lane order, whereas the develop operation does the inverse. The compress operation is helpful in filtering question outcomes.
  In one other addition to the vector API, bitwise integral lanewise operations could be expanded, together with operations such counting the variety of one bits, reversing the order of bits, and compressing and increasing bits. Objectives of the API included being clear and concise, platform-agnostic, having dependable runtime and compilation efficiency on x64 and AArch64 architectures, and enabling “swish” degradation, for conditions by which a vector computation can’t be absolutely expressed at runtime as a sequence of vector operations.
• With the Linux/RISC-V port, Java would acquire help for a {hardware} instruction set that’s already supported by a variety of language toolchains. RISC-V truly is a household of associated ISAs. The Linux/RISC-V port would solely help the RV64GV configuration of RISC-V, a common objective 64-bit ISA that features vector directions. The builders of Java might think about different RISC-V configurations sooner or later.

The port would help the next HotSpot VM choices: the template interpreter, C1 (shopper) JIT compiler, C2 (server) JIT compiler, and all present mainline rubbish collectors together with ZGC and Shenandoah. The precise porting is almost full; the main focus of the JDK Enhancement Proposal (JEP) is integration of the port into the JDK mainline repository.

Like JDK 18, JDK 19 is because of be a short-term launch, with solely six months of top-level, Premier help.

The previous launch, JDK 17, was a Lengthy Time period Assist (LTS) launch, with a number of years of help. It arrived September 14, 2021.