Java static synchronization

The Java static synchronization is a mechanism that allows multiple threads to synchronize access to static methods or static data members of a class. When a method or a block is declared as static synchronized, it means that the lock acquired by the synchronization is associated with the class itself, rather than with an instance of the class. This ensures that only one thread can execute the static synchronized method or block at a time, regardless of the number of instances of the class.

Static synchronization is useful when multiple threads need to access or modify shared static data, and you want to avoid potential race conditions and data inconsistencies. It helps in maintaining data integrity and ensuring thread safety in situations where multiple threads may attempt to modify the same static data concurrently.

Here’s an example to illustrate the concept of static synchronization:

public class StaticSynchronizationExample {
    private static int counter = 0;

    public static synchronized void increment() {
        counter++;
    }

    public static void main(String[] args) {
        Runnable runnable = () -> {
            for (int i = 0; i < 5; i++) {
                increment();
                System.out.println(Thread.currentThread().getName() + " - Counter: " + counter);
            }
        };

        // Create and start multiple threads
        Thread thread1 = new Thread(runnable, "Thread 1");
        Thread thread2 = new Thread(runnable, "Thread 2");
        thread1.start();
        thread2.start();
    }
}

We have a StaticSynchronizationExample class with a static data member counter and a static method increment(). The increment() method is declared as static synchronized, meaning that only one thread can execute this method at a time.

In the main method, we create two threads (thread1 and thread2) that call the increment() method. Since the increment() method is synchronized, only one thread can increment the counter variable at any given time, ensuring that the updates to the shared static data are performed in a thread-safe manner.

Static synchronization comes with a trade-off. While it ensures thread safety for static methods and data, it may also introduce contention if many threads frequently access the same synchronized static method. In such cases, the performance of the application may be impacted due to the locking overhead. Therefore, it’s essential to use static synchronization judiciously and consider other synchronization techniques based on the specific requirements of your application.

The static synchronization in Java allows you to synchronize access to static methods and static data members, ensuring thread safety when multiple threads interact with shared static resources. It is a valuable tool to maintain data consistency and prevent data corruption in multithreaded environments. However, it should be used carefully to avoid potential performance bottlenecks.