1. Pattern Matching for Primitive Types in instanceof and switch (JEP 488)

Previously, Java’s pattern matching worked only with objects, requiring explicit casting when dealing with primitives. Java SE 24 extends this functionality to primitive types, allowing more concise and readable code in instanceof checks and switch statements.

Example: Using instanceof with primitives

static void process(Object obj) {
    if (obj instanceof Integer i) {
        System.out.println("Integer: " + (i * 2));
    } else if (obj instanceof Double d) {
        System.out.println("Double: " + (d / 2));
    } else {
        System.out.println("Unknown type");
    }
}

public static void main(String[] args) {
    process(10);   // Output: Integer: 20
    process(5.5);  // Output: Double: 2.75
}Code language: JavaScript (javascript)

Before this update, handling different numeric types required manual casting.

Example: Using switch with primitives

static void checkNumber(Number num) {
    switch (num) {
        case Integer i -> System.out.println("Integer: " + (i * 2));
        case Double d -> System.out.println("Double: " + (d / 2));
        default -> System.out.println("Other number type");
    }
}Code language: JavaScript (javascript)

This reduces verbosity and improves performance by eliminating unnecessary conversions.

2. Simplified Module Imports

Java SE 24 introduces module import declarations, allowing all public packages of a module to be imported at once. This feature is particularly useful for projects that use Java modules but don’t want to specify individual package imports.

Example: Importing all packages from a module

import java.base.*;

public class Main {
    public static void main(String[] args) {
        System.out.println("Simplified module imports!");
    }
}Code language: JavaScript (javascript)

This makes working with modular Java applications smoother and less cluttered.

3. More Flexible Constructor Rules (Third Preview)

Previously, explicit constructor calls (this(…) or super(…)) had to be the first statement inside a constructor. With Java 24, initialization code can now appear before calling another constructor, offering greater flexibility in designing class constructors.

Example: Initializing a field before calling another constructor

class Person {
    String name;
    int age;

    Person(String name) {
        System.out.println("Setting name before"+ 
          "constructor chaining...");
        this.name = name;
        this(25); // Calls another constructor after setting the name
    }

    Person(int age) {
        this.age = age;
        System.out.println("Person initialized with age: " + age);
    }
}

public class Main {
    public static void main(String[] args) {
        Person p = new Person("Alice");
    }
}Code language: JavaScript (javascript)

This change provides developers with more freedom in structuring their constructors.

4. Simpler Java Programs with Instance Main Methods

Java SE 24 simplifies writing small programs by reducing the need for boilerplate code. Now, developers can define a main method without wrapping it inside a class.

Example: Running a Java program without a class

Instead of the traditional:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, Java 24!");
    }
}Code language: JavaScript (javascript)

You can now write:

void main() {
    System.out.println("Hello, Java 24!");
}Code language: JavaScript (javascript)

This makes Java more beginner-friendly and speeds up prototyping.

5. Key Derivation Functions for Secure Cryptography (JEP 478)

Java SE 24 introduces built-in support for Key Derivation Functions (KDFs), which are essential for securely generating cryptographic keys from passwords or other secret values.

Example: Deriving a cryptographic key from a password

import java.security.*;
import javax.crypto.SecretKey;
import javax.crypto.spec.PBEKeySpec;

public class KDFExample {
    public static void main(String[] args) throws Exception {
        String password = "securePass";
        byte[] salt = {1, 2, 3, 4, 5};

        PBEKeySpec spec = new PBEKeySpec(password.toCharArray(), salt, 10000, 256);
        SecretKey key = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256").generateSecret(spec);

        System.out.println("Derived Key: " + new String(key.getEncoded()));
    }
}Code language: JavaScript (javascript)

This helps improve security, especially in applications that need to securely store user credentials or encryption keys.

6. Scoped Values for Safer Data Sharing (Fourth Preview)

Scoped values provide a way to share immutable data within a thread and its child threads, offering a safer alternative to ThreadLocal.

Example: Using Scoped Values in Multithreading

import jdk.incubator.concurrent.ScopedValue;

public class ScopedValueExample {
    private static final ScopedValue<String> USER = ScopedValue.newInstance();

    public static void main(String[] args) {
        ScopedValue.where(USER, "Alice").run(() -> {
            greetUser();
        });
    }

    static void greetUser() {
        System.out.println("Hello, " + USER.get());
    }
}Code language: JavaScript (javascript)

Unlike ThreadLocal, this approach prevents memory leaks and improves performance in concurrent applications.

7. Performance Boost with Vector API (Seventh Incubator)

The Vector API allows developers to write high-performance code by utilizing SIMD (Single Instruction, Multiple Data) operations, which execute multiple computations in parallel.

Example: Using the Vector API for fast numerical processing

import jdk.incubator.vector.*;

public class VectorExample {
    public static void main(String[] args) {
        float[] numbers = {1.0f, 2.0f, 3.0f, 4.0f};
        FloatVector vector = FloatVector.fromArray(FloatVector.SPECIES_128, numbers, 0);

        FloatVector result = vector.add(5.0f);
        result.intoArray(numbers, 0);

        for (float f : numbers) {
            System.out.println(f); // Outputs 6.0, 7.0, 8.0, 9.0
        }
    }
}Code language: JavaScript (javascript)

This feature is especially useful for applications that require heavy mathematical calculations, such as graphics rendering or machine learning

8. Stronger Security with Quantum-Resistant Cryptography

With the rise of quantum computing, traditional encryption methods may become vulnerable. Java SE 24 introduces quantum-resistant cryptographic algorithms, such as Dilithium and Kyber, to help future-proof applications.

Example: Generating a quantum-resistant key pair

import java.security.*;

public class QuantumSecureExample {
    public static void main(String[] args) throws Exception {
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("Dilithium");
        kpg.initialize(256);
        KeyPair kp = kpg.generateKeyPair();

        System.out.println("Quantum-secure key pair generated!");
    }
}Code language: JavaScript (javascript)

This helps protect sensitive data against potential quantum attacks in the future.

Final Thoughts

Java SE 24 continues to evolve by enhancing security, improving performance, and simplifying development workflows. Some of the key takeaways include:

✅ More concise pattern matching with primitive types

✅ Better constructor flexibility

✅ Streamlined cryptographic APIs for security

✅ Improved concurrency support with Scoped Values

✅ Higher performance for parallel computations