8 Little‑Known Java APIs That Can Supercharge Your Code

8. Phaser

The Phaser class, similar to CountDownLatch but more flexible, allows dynamic registration of parties and coordination across multiple phases.

Phaser phaser = new Phaser(50);
Runnable r = () -> {
    System.out.println("phase-0");
    phaser.arriveAndAwaitAdvance();
    System.out.println("phase-1");
    phaser.arriveAndAwaitAdvance();
    System.out.println("phase-2");
    phaser.arriveAndDeregister();
};
ExecutorService executor = Executors.newFixedThreadPool(50);
for (int i = 0; i < 50; i++) {
    executor.submit(r);
}