/Java/Java 19

Java 19 APIs & Features

Java 19 marks a significant milestone in concurrent programming with the introduction of Virtual Threads as a preview feature, representing a revolutionary shift toward lightweight, high-throughput concurrency. This release also advances pattern matching capabilities, introduces record patterns, and continues development of the Vector API for high-performance computing.

Released: September 2022

Standard Release

Other Java Versions

Java 19 Overview

Release Information

Release Date:

September 2022

Support Type:

Standard Release

Quick Summary

Top Features

Virtual Threads (Preview) - Revolutionary lightweight concurrency with Project Loom
Pattern Matching for switch (Third Preview) - Enhanced switch expressions with patterns
Vector API (Third Incubator) - SIMD operations for high-performance computing
Foreign Function & Memory API (Preview) - Safe native code interoperability
Structured Concurrency (Incubator) - Simplified concurrent programming patterns
Record Patterns (Preview) - Pattern matching with record deconstruction

API Examples

Virtual Threads (Preview)

Java 19 introduces Virtual Threads as a preview feature, representing a revolutionary approach to concurrent programming. Virtual Threads provide lightweight, high-throughput threads that can handle millions of concurrent operations efficiently, eliminating the traditional thread-per-request model limitations and enabling scalable applications with minimal resource overhead.

import java.util.concurrent.Executors;
import java.time.Duration;

// Create virtual threads
Thread virtualThread = Thread.ofVirtual()
    .name("virtual-thread")
    .start(() -> {
        System.out.println("Running in virtual thread: " + 
            Thread.currentThread().getName());
    });

// Virtual thread executor
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
    // Submit 10,000 tasks - each runs in its own virtual thread
    for (int i = 0; i < 10_000; i++) {
        final int taskId = i;
        executor.submit(() -> {
            try {
                Thread.sleep(Duration.ofSeconds(1));
                System.out.println("Task " + taskId + " completed");
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        });
    }
}

// Traditional vs Virtual Thread performance
// Traditional threads (limited by OS)
try (var platformExecutor = Executors.newFixedThreadPool(200)) {
    // Can only handle ~1000 concurrent tasks efficiently
}

// Virtual threads (JVM managed)
try (var virtualExecutor = Executors.newVirtualThreadPerTaskExecutor()) {
    // Can handle millions of concurrent tasks
}

Record Patterns (Preview)

Java 19 introduces Record Patterns as a preview feature, enabling pattern matching with record destructuring in switch expressions and instanceof checks. This feature allows developers to extract and match against record components directly, making code more readable and eliminating the need for manual field access and null checks.

// Define records
public record Point(int x, int y) {}
public record Rectangle(Point topLeft, Point bottomRight) {}

// Pattern matching with record destructuring
public void processShape(Object shape) {
    switch (shape) {
        case Rectangle(Point(int x1, int y1), Point(int x2, int y2)) -> {
            System.out.println("Rectangle from (" + x1 + "," + y1 + 
                ") to (" + x2 + "," + y2 + ")");
            int area = (x2 - x1) * (y2 - y1);
            System.out.println("Area: " + area);
        }
        case Point(int x, int y) -> {
            System.out.println("Point at (" + x + "," + y + ")");
        }
        default -> System.out.println("Unknown shape");
    }
}

// Nested record patterns
public record Person(String name, Address address) {}
public record Address(String street, String city) {}

public void processPersons(Object obj) {
    switch (obj) {
        case Person(String name, Address(String street, String city)) -> {
            System.out.println(name + " lives at " + street + ", " + city);
        }
        default -> System.out.println("Not a person");
    }
}

Vector API (Third Incubator)

Java 19 continues development of the Vector API as an incubator feature, providing SIMD (Single Instruction, Multiple Data) operations for high-performance computing. This API enables developers to write vectorized code that can leverage CPU vector instructions, significantly improving performance for mathematical computations, data processing, and scientific applications.

import jdk.incubator.vector.*;

// Vector operations for high-performance computing
public class VectorExample {
    static final VectorSpecies<Float> SPECIES = FloatVector.SPECIES_PREFERRED;
    
    public static void vectorAdd(float[] a, float[] b, float[] c) {
        int i = 0;
        int upperBound = SPECIES.loopBound(a.length);
        
        for (; i < upperBound; i += SPECIES.length()) {
            FloatVector va = FloatVector.fromArray(SPECIES, a, i);
            FloatVector vb = FloatVector.fromArray(SPECIES, b, i);
            FloatVector vc = va.add(vb);
            vc.intoArray(c, i);
        }
        
        // Handle remaining elements
        for (; i < a.length; i++) {
            c[i] = a[i] + b[i];
        }
    }
    
    public static float vectorSum(float[] array) {
        FloatVector sum = FloatVector.zero(SPECIES);
        int i = 0;
        int upperBound = SPECIES.loopBound(array.length);
        
        for (; i < upperBound; i += SPECIES.length()) {
            FloatVector va = FloatVector.fromArray(SPECIES, array, i);
            sum = sum.add(va);
        }
        
        float result = sum.reduceLanes(VectorOperators.ADD);
        
        // Handle remaining elements
        for (; i < array.length; i++) {
            result += array[i];
        }
        
        return result;
    }
}