GeezerVison is showing javaevolved.dev — RandomGenerator interface | java.evolved

Home / Security / RandomGenerator interface

Security Intermediate

RandomGenerator interface

Use the RandomGenerator interface to choose random number algorithms by name without coupling to a specific class.

Code Comparison

✕ Java 8

// Hard-coded to one algorithm
Random rng = new Random();
int value = rng.nextInt(100);

// Or thread-local, but still locked in
int value = ThreadLocalRandom.current()
    .nextInt(100);

✓ Java 17+

// Algorithm-agnostic via factory
var rng = RandomGenerator.of("L64X128MixRandom");
int value = rng.nextInt(100);

// Or get a splittable generator
var rng = RandomGeneratorFactory
    .of("L64X128MixRandom").create();

Share 𝕏

See a problem with this code? Let us know.

Why the modern way wins

🔧

Algorithm-agnostic

Choose the best RNG algorithm by name without changing code structure.

⚡

Better algorithms

Access to modern LXM generators with superior statistical properties.

🔗

Unified API

One interface covers Random, ThreadLocalRandom, SplittableRandom, and more.

Old Approach

new Random() / ThreadLocalRandom

Modern Approach

RandomGenerator factory

Since JDK

Difficulty

Intermediate

JDK Support

RandomGenerator interface

Available

Available since JDK 17 (September 2021, JEP 356).

How it works

JDK 17 introduced RandomGenerator as a common interface for all RNG implementations. Instead of hard-coding new Random() or ThreadLocalRandom, you can select algorithms by name via a factory, making it easy to swap between algorithms optimized for different use cases (speed, statistical quality, splittability).

Strong random generation

Java 8

// Default algorithm — may not be
// the strongest available
SecureRandom random =
    new SecureRandom();
byte[] bytes = new byte[32];
random.nextBytes(bytes);

Java 9+

// Platform's strongest algorithm
SecureRandom random =
    SecureRandom.getInstanceStrong();
byte[] bytes = new byte[32];
random.nextBytes(bytes);

Hover to see modern ➜

JDK 9+ →

Security Advanced

Key Derivation Functions

Java 8

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

Java 25

var kdf = KDF.getInstance("HKDF-SHA256");
SecretKey key = kdf.deriveKey(
    "AES",
    KDF.HKDFParameterSpec
        .ofExtract()
        .addIKM(inputKey)
        .addSalt(salt)
        .thenExpand(info, 32)
        .build()
);

Hover to see modern ➜

JDK 25+ →

Concurrency Beginner

Virtual threads

Java 8

Thread thread = new Thread(() -> {
    System.out.println("hello");
});
thread.start();
thread.join();

Java 21+

Thread.startVirtualThread(() -> {
    IO.println("hello");
}).join();

Hover to see modern ➜

JDK 21+ →