Advanced Java Concurrency Utilities

Java provides a robust set of concurrency utilities that can help developers manage multi-threaded programming more effectively. Beyond the basic synchronized and volatile keywords, advanced utilities such as Phaser, StampedLock, and Exchanger offer more sophisticated control over thread coordination and synchronization.

What are Advanced Java Concurrency Utilities?

Advanced Java concurrency utilities are part of the java.util.concurrent package, designed to facilitate complex synchronization scenarios and enhance the performance of concurrent applications. These utilities provide higher-level abstractions for common concurrency patterns, making it easier to implement thread-safe operations.

Key Advanced Concurrency Utilities

1. Phaser:

   • Use Case: Phaser is a flexible synchronization barrier that can be used to coordinate multiple threads performing phased activities.
   • Example:

    import java.util.concurrent.Phaser;
   
    public class PhaserExample {
        public static void main(String[] args) {
            Phaser phaser = new Phaser(1); // Register the main thread
   
            for (int i = 0; i < 3; i++) {
                new Thread(new Worker(phaser)).start();
            }
   
            phaser.arriveAndDeregister(); // Deregister the main thread
        }
    }
   
    class Worker implements Runnable {
        private Phaser phaser;
   
        Worker(Phaser phaser) {
            this.phaser = phaser;
            this.phaser.register();
        }
   
        @Override
        public void run() {
            System.out.println(Thread.currentThread().getName() + " working in phase 1");
            phaser.arriveAndAwaitAdvance();
   
            System.out.println(Thread.currentThread().getName() + " working in phase 2");
            phaser.arriveAndAwaitAdvance();
   
            phaser.arriveAndDeregister();
        }
    }
   

2. StampedLock:

   • Use Case: StampedLock is a capability-based lock with three modes for controlling read/write access: writing, reading, and optimistic reading.
   • Example:

    import java.util.concurrent.locks.StampedLock;
   
    public class StampedLockExample {
        private final StampedLock lock = new StampedLock();
        private int count = 0;
   
        public void increment() {
            long stamp = lock.writeLock();
            try {
                count++;
            } finally {
                lock.unlockWrite(stamp);
            }
        }
   
        public int getCount() {
            long stamp = lock.tryOptimisticRead();
            int currentCount = count;
            if (!lock.validate(stamp)) {
                stamp = lock.readLock();
                try {
                    currentCount = count;
                } finally {
                    lock.unlockRead(stamp);
                }
            }
            return currentCount;
        }
   
        public static void main(String[] args) {
            StampedLockExample example = new StampedLockExample();
            example.increment();
            System.out.println("Count: " + example.getCount());
        }
    }
   

3. Exchanger:

   • Use Case: Exchanger is a synchronization point at which threads can exchange objects.
   • Example:

    import java.util.concurrent.Exchanger;
   
    public class ExchangerExample {
        public static void main(String[] args) {
            Exchanger<String> exchanger = new Exchanger<>();
   
            new Thread(() -> {
                try {
                    String data = "Thread 1 data";
                    data = exchanger.exchange(data);
                    System.out.println("Thread 1 received: " + data);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }).start();
   
            new Thread(() -> {
                try {
                    String data = "Thread 2 data";
                    data = exchanger.exchange(data);
                    System.out.println("Thread 2 received: " + data);
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }).start();
        }
    }
   

Conclusion

Advanced concurrency utilities in Java provide powerful tools for managing complex multi-threaded scenarios. By leveraging utilities like Phaser, StampedLock, and Exchanger, developers can create more efficient, scalable, and maintainable concurrent applications.