Java 18 is Now Available

Oracle has released version 18 of the Java programming language and virtual machine. The nine (9) JEPs in this final feature set are:

• JEP 400: UTF-8 by Default
• JEP 408: Simple Web Server
• JEP 413: Code Snippets in Java API Documentation
• JEP 416: Reimplement Core Reflection with Method Handles
• JEP 417: Vector API (Third Incubator)
• JEP 418: Internet-Address Resolution SPI
• JEP 419: Foreign Function & Memory API (Second Incubator)
• JEP 420: Pattern Matching for switch (Second Preview)
• JEP 421: Deprecate Finalization for Removal

The feature cadence for Java 18 is slightly lower than previous releases as compared to: 14 features in Java 17; 17 features in Java 16; 14 features in Java 15; and 16 features in Java 14.

This release features JEPs that provide continued contribution toward Project Amber, Project Loom and Project Panama along with some useful new tools. We examine a few of these new features here.

Project Panama

JEP 417 and JEP 419 fall under the auspices of Project Panama, a project designed to improve and enrich interoperability between the JVM and well-defined "foreign," i.e., non-Java, APIs that will most-likely include interfaces commonly used within C libraries.

Along with performance improvements, JEP 417, Vector API (Third Incubator), incorporates enhancements in response to feedback from the previous two rounds of incubation: JEP 414, Vector API (Second Incubator) (delivered in JDK 17), and JEP 338, Vector API (Incubator), delivered as an incubator module in JDK 16.

JEP 419, Foreign Function & Memory API (Second Incubator), evolves the first incubator, JEP 412, Foreign Function & Memory API (Incubator), delivered in JDK 17, to incorporate improvements based on Java community feedback. Changes in this second incubator include: support for more carriers in memory access var handles such as boolean and MemoryAddress interface; a more general dereference API for the MemoryAddress and MemorySegment interfaces; a simpler API to obtain downcall methods handles such that passing a MemoryType enumeration is no longer necessary; and a new API to copy Java arrays to and from memory segments.

Project Loom

JEP 418 falls under the auspices of Project Loom, a project designed to explore, incubate and deliver Java VM features and APIs built for the purpose of supporting easy-to-use, high-throughput lightweight concurrency and new programming models. This would be accomplished via virtual threads, delimited continuations and tail calls.

JEP 418, Internet-Address Resolution SPI, defines a service-provider interface for host name and address resolution, so that java.net.InetAddress may take advantage of resolvers other than the default built-in OpenJDK resolver.

Project Amber

JEP 420 falls under the auspices of Project Amber, a project designed to explore and incubate smaller Java language features to improve productivity.

JEP 420, Pattern Matching for switch (Second Preview), allows a target switch expression to be tested against a number of patterns, each with a specific action, allowing complex data-oriented queries to be expressed concisely and safely. This is the second preview following JEP 406, Pattern Matching for switch (Preview), that was delivered in JDK 17. Enhancements include: an improvement in dominance checking that forces a constant case label to appear before a guarded pattern of the same type; and an exhaustiveness checking of the switch block is now more precise with sealed hierarchies.

Java Tools

JEP 413, Code Snippets in Java API Documentation, introduces the @snippet tag for Oracle's Standard Doclet, the well-known Java API documentation utility that produces the default HTML-formatted output. The intent is to simplify the inclusion of example source code in API documentation. Code snippets may be inline or external as the following two examples will demonstrate:

In this inline example, the source code is added to the comments preceded by the @snippet tag and wrapped in curly braces:

    
/**
 * The following code shows how to use {@code Optional.isPresent}:
 * {@snippet :
 * if (v.isPresent()) {
 *     System.out.println("v: " + v.get());
 *     }
 * }
 */
    

In this external example, an existing source file, ShowOptional.java, contains @start and @end tags. A defined region, i.e, region="example" is referenced in the comments and in the source file:

    
/**
 * The following code shows how to use {@code Optional.isPresent}:
 * {@snippet file="ShowOptional.java" region="example"}
 */

public class ShowOptional {
    void show(Optional<String> v) {
        // @start region="example"
        if (v.isPresent()) {
            System.out.println("v: " + v.get());
            }
        // @end
        }
    }
    

JEP 408, Simple Web Server, provides a minimal HTTP command-line web server that serves only static files. This utility is designed to be useful for prototyping, ad-hoc coding, and testing, particularly in an educational environment. The server may be started as follows:

    
java -m jdk.httpserver [-b bind address] [-p port] [-d directory] [-h to show help message] [-o none|default|verbose]
    

Java 19

Currently, only one JEP is Targeted or Integrated for inclusion in Java 19:

• JEP 422: Linux/RISC-V Port

The formal release date for Java 19 has not yet been announced, but it is expected to be delivered in mid-September 2022 as per the six-month release cadence. Developers can anticipate a feature freeze in mid-June 2022.

Java 18 may now be downloaded from Oracle with binaries from other vendors expected to become available in the coming days.