JDK 23: Features, Enhancements, and Comparisons

1. Virtual Threads

JDK 23 introduces significant improvements to the concurrency model with virtual threads. Virtual threads are lightweight threads that can scale to millions, helping Java applications handle concurrent workloads more efficiently. This feature is part of Project Loom, aiming to make it easier to write highly scalable, concurrent applications.

Key Benefits:

• High scalability with low memory overhead.
• Reduces the complexity of working with concurrency.
• Improves application performance under heavy concurrent loads.

Example:

import java.util.concurrent.*;

public class VirtualThreadsExample {
    public static void main(String[] args) throws InterruptedException {
        ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor();
        for (int i = 0; i < 5; i++) {
            executor.submit(() -> {
                System.out.println("Running in virtual thread: " + Thread.currentThread().getName());
            });
        }
        executor.shutdown();
        executor.awaitTermination(1, TimeUnit.MINUTES);
    }
}
        

2. Pattern Matching for Switch (Preview)

Pattern matching for switch, introduced as a preview feature in JDK 23, allows developers to use more powerful and flexible patterns in switch statements. This enhancement makes it easier to write concise and type-safe code, reducing the need for complex if-else chains.

Comparison with Previous Versions:

• Prior to JDK 23, switch statements only supported basic value matching.
• JDK 23 introduces the ability to match complex patterns, including types and conditions.

Example:

public class PatternMatchingExample {
    static String getType(Object obj) {
        return switch (obj) {
            case Integer i -> "Integer: " + i;
            case String s -> "String: " + s;
            case null -> "Null";
            default -> "Unknown";
        };
    }

    public static void main(String[] args) {
        System.out.println(getType(42)); // Integer: 42
        System.out.println(getType("Hello")); // String: Hello
        System.out.println(getType(null)); // Null
    }
}
        

3. Record Patterns (Preview)

Record patterns, also introduced as a preview feature in JDK 23, enhance the record feature by allowing pattern matching on record types. This helps developers easily destructure and extract values from records in a concise and readable manner.

Key Benefits:

• Improves readability and maintainability of code.
• Enhances destructuring capabilities for record types.

Example:

public class RecordPatternExample {
    record Person(String name, int age) {}

    static String extractName(Object obj) {
        if (obj instanceof Person(String name, int age)) {
            return name;
        }
        return "Unknown";
    }

    public static void main(String[] args) {
        Person p = new Person("Alice", 30);
        System.out.println(extractName(p)); // Alice
    }
}
        

4. Foreign Function & Memory API (Incubator)

JDK 23 enhances the Foreign Function & Memory API, which was first incubated in JDK 14. This API allows Java programs to safely interact with native code, offering better control over native memory while ensuring safety and performance improvements.

Key Benefits:

• Provides a more secure way to access and manage native memory.
• Enables high-performance interaction with non-Java code.

Example:

import java.foreign.*;

public class ForeignFunctionExample {
    public static void main(String[] args) {
        // Example usage (this is a conceptual demo as full code requires JNI)
        try (MemorySegment segment = MemorySegment.allocateNative(1024)) {
            System.out.println("Memory allocated at: " + segment.address());
        }
    }
}
        

5. Sealed Interfaces (JEP 409)

Sealed interfaces, introduced in JDK 23 under JEP 409, provide the ability to control which classes or interfaces can implement or extend a given interface. This feature improves the maintainability of large codebases by restricting inheritance to a known set of subclasses.

Example:

public sealed interface Shape permits Circle, Rectangle {}

public final class Circle implements Shape {
    private final int radius;
    public Circle(int radius) { this.radius = radius; }
}

public final class Rectangle implements Shape {
    private final int length, width;
    public Rectangle(int length, int width) { this.length = length; this.width = width; }
}
        

Conclusion

JDK 23 introduces several exciting features, including virtual threads for scalable concurrency, pattern matching for switch, and improved foreign function capabilities. These updates enhance developer productivity, performance, and the overall ease of working with Java. If you're coming from previous versions of JDK, the improvements in JDK 23 are compelling and worth exploring.

For more information, check out these resources:

• Official JDK 23 Release Notes
• Project Loom Overview