What methods and tools are used in Java to implement thread synchronization?

In Java, several main methods and tools are used for thread synchronization:

• The synchronized keyword — allows making a block of code or a method a critical section, ensuring that only one thread executes this code at a time.

• Objects from the java.util.concurrent package:

  • ReentrantLock — a more flexible alternative to synchronized with the ability to attempt lock acquisition, timeouts, etc.
  • Semaphore, CountDownLatch, CyclicBarrier — for more complex thread coordination.

• Classes for atomic operations from java.util.concurrent.atomic (e.g., AtomicInteger) — allow performing operations without locks.

• Volatile variables — guarantee visibility of variable changes between threads, but do not ensure atomicity.

Example of using synchronized:

public class Counter {
    private int count = 0;

    public synchronized void increment() {
        count++;
    }

    public synchronized int getCount() {
        return count;
    }
}

This code guarantees that increment and read operations on the counter are thread-safe.