What is New in JDK 24?

Java Development Kit 24 (JDK 24) continues Java’s evolution with new language features, performance improvements, and enhanced APIs. This release focuses on productivity, performance, and modernizing the platform for developers. Let’s dive into the key updates, complete with code examples.

1. Language Enhancements

1.1. Unnamed Variables and Patterns (Preview)

Use _ to ignore variables or patterns you don’t need, improving code readability.

// Unnamed variable in a loop
for (String _ : List.of("a", "b", "c")) {
    System.out.println("Processing...");
}

// Unnamed pattern in instanceof
if (obj instanceof Integer _) {
    System.out.println("It's an Integer!");
}

Note. Enable preview features with --enable-preview.

1.2. Primitive Types in Patterns and switch (Preview)

Pattern matching now supports primitive types in instanceof and switch expressions.

Object value = 42;

switch (value) {
    case int i -> System.out.println("int: " + i);
    case double d -> System.out.println("double: " + d);
    default -> System.out.println("Unsupported type");
}

1.3. String Templates (Second Preview)

Embed expressions in strings using STR for safer and cleaner formatting.

String name = "Alice";
int age = 30;
String message = STR."Hello, \{name}. You are \{age} years old.";
System.out.println(message); // Output: Hello, Alice. You are 30 years old.

2. API and Library Updates

2.1. Scoped Values (Second Preview)

A safer alternative to thread-local variables for managing contextual data.

final ScopedValue<String> USER = ScopedValue.newInstance();

ScopedValue.where(USER, "admin").run(() -> {
    System.out.println(USER.get()); // Output: admin
});

2.2. Foreign Function & Memory API (Third Preview)

Interact with native code and off-heap memory efficiently.

// Allocate off-heap memory
try (MemorySession session = MemorySession.openConfined()) {
    MemorySegment segment = MemorySegment.allocateNative(100, session);
    // Use the memory segment...
}

3. Performance Improvements

3.1. Faster Class-File Processing

JDK 24 optimizes class-file reading, speeding up builds for large projects.

Impact: Tools like Maven, Gradle, and IDEs benefit from reduced startup times.

3.2. Enhanced Garbage Collection

ZGC (Z Garbage Collector) now handles larger heaps with lower latency.

4. Deprecations and Removals

• Deprecated: Legacy APIs like finalize() in java.lang.Object.
• Removed: Older garbage collectors (e.g., Concurrent Mark Sweep) to simplify the JVM.

5. Getting Started with JDK 24

5.1. Download JDK 24

Get the latest build from jdk.java.net/24.

5.2. Compile with Preview Features

Use --enable-preview to test new language features:

javac --enable-preview --release 24 Main.java
java --enable-preview Main

Example. Full Application Using JDK 24 Features

import java.util.List;
import java.util.stream.IntStream;

public class JDK24Demo {
    public static void main(String[] args) {
        // String Templates
        String user = "Bob";
        int score = 95;
        System.out.println(STR."\{user} scored \{score}%");

        // Pattern Matching for Primitives
        Object data = 3.14;
        switch (data) {
            case Integer i -> System.out.println("Integer: " + i);
            case Double d -> System.out.println("Double: " + d);
            default -> System.out.println("Unknown");
        }

        // Unnamed Variables
        IntStream.range(0, 5).forEach(_ -> System.out.println("Hello!"));
    }
}

Output

Why Upgrade to JDK 24?

• Cleaner Code: Unnamed variables and patterns reduce clutter.
• Performance: Faster class-file processing and GC improvements.
• Future-Proof: Preview features like Scoped Values prepare you for upcoming stable releases.

Conclusion

JDK 24 reinforces Java’s commitment to developer productivity and modern application demands. With features like primitive type pattern matching, string templates, and scoped values, Java continues to evolve while maintaining backward compatibility. Explore these updates today to write cleaner, safer, and more efficient code.