Concurrency control is an essential aspect of writing robust and efficient concurrent programs. It helps ensure that multiple threads can access shared resources without causing data inconsistencies or race conditions. In Java, there are several mechanisms available for implementing concurrency control. In this blog post, we will explore some common techniques using Java objects.

1. Synchronized Keyword

The synchronized keyword in Java ensures that only one thread can execute a synchronized block or method for a given object. It prevents concurrent access to critical sections of code and provides mutual exclusion.

class Counter {
  private int count;

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

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

In the example above, the increment() and getCount() methods are synchronized, ensuring that only one thread can execute them at a time. This prevents race conditions when multiple threads attempt to modify or access the count variable simultaneously.

2. ReentrantLock Class

The ReentrantLock class is an alternative to using the synchronized keyword. It provides more flexibility and control over a lock. It supports features like fairness, interruptibility, and timed waiting.

import java.util.concurrent.locks.ReentrantLock;

class Counter {
  private int count;
  private ReentrantLock lock = new ReentrantLock();

  public void increment() {
    lock.lock();
    try {
      count++;
    } finally {
      lock.unlock();
    }
  }

  public int getCount() {
    lock.lock();
    try {
      return count;
    } finally {
      lock.unlock();
    }
  }
}

In the example above, we use an instance of ReentrantLock to control access to the increment() and getCount() methods. The lock() method acquires the lock, and the unlock() method releases it. The finally block ensures that the lock is always released, even if an exception occurs.

Conclusion

Concurrency control is crucial in multi-threaded applications to avoid data inconsistencies and race conditions. In Java, we can implement concurrency control mechanisms using the synchronized keyword or the ReentrantLock class. These mechanisms help ensure that only one thread can access critical sections of code at a time, providing mutual exclusion and preventing data corruption.

By utilizing the synchronized keyword or the ReentrantLock class, developers can effectively manage concurrent access to shared resources, facilitating smoother execution of multi-threaded Java applications.

#Java #Concurrency