Synchronized Methods in Java:

In a multithreaded Java environment, when multiple threads access shared resources concurrently, it can lead to race conditions and data inconsistencies.

 Synchronized methods provide a way to ensure thread safety by allowing only one thread to execute the synchronized method at a time. 

This is achieved by acquiring an intrinsic lock (monitor) associated with the object's instance to which the method belongs.


Syntax of Declaring a Synchronized Method:

To declare a method as synchronized, you simply add the synchronized keyword before the method's return type in the method declaration. 

The synchronized keyword indicates that only one thread can execute this method at any given time, regardless of the number of objects (instances) of the class.


public synchronized void methodName() { 
// Synchronized method body

    // Only one thread can execute this method at a time 
// Critical operations on shared data should be performed inside this method
}

Example:

Let's create a simple class called Counter that contains a shared count variable.

We'll declare the increment() method as synchronized to ensure thread-safe access to the count.


class Counter {
private int count = 0;
public synchronized void increment() {
 count++;
 }
public int getCount() {
return count; 
 } 
}

In this example, the increment() method is declared as synchronized. This ensures that when multiple threads call the increment() method concurrently, only one thread can execute it at a time, preventing race conditions.


Using Synchronized Methods for Thread Safety:

Let's see the behavior of synchronized methods by creating multiple threads that increment the counter simultaneously.


public class Main { 
public static void main(String[] args) { 
Counter counter = new Counter(); 
Runnable task = () -> {
for (int i = 0; i < 10000; i++) { 
 counter.increment();
            } 
 };
Thread thread1 = new Thread(task); 
Thread thread2 = new Thread(task); 
 thread1.start();
 thread2.start();

        // Wait for both threads to complete 
try { 
 thread1.join(); 
 thread2.join(); 
 } catch (InterruptedException e) { 
 e.printStackTrace();
 }

        System.out.println("Final Count: " + counter.getCount());
    }
}

In this example, we create two threads (thread1 and thread2) that share the same Counter object. Both threads execute the increment() method concurrently 10,000 times.


Thanks to the synchronized method, only one thread is allowed to execute the increment() method at a time, ensuring that each increment operation is performed atomically and without interference from other threads.


Benefits of Synchronized Methods:

Thread Safety: Synchronized methods ensure that shared resources are accessed safely by multiple threads, avoiding race conditions and data corruption.

Simplicity: The synchronized keyword provides a simple and straightforward approach to handle concurrency in Java applications. The locking mechanism is handled implicitly by the JVM.

Built-in Locking: The JVM automatically manages the locking and unlocking of the object's monitor, reducing the risk of errors in manual synchronization.


Considerations:

Performance Overhead: While synchronized methods ensure thread safety, excessive use of synchronization can lead to performance overhead due to contention for locks. Consider using synchronized blocks for more granular control when necessary.

Deadlock Avoidance: Avoid nested synchronized method calls to prevent potential deadlocks where threads wait indefinitely for each other to release locks.


Conclusion:

Synchronized methods are a powerful tool in Java for achieving thread safety and preventing race conditions in multithreaded applications.

 By synchronizing critical methods, you ensure that only one thread can execute them at a time, protecting shared data from concurrent access and maintaining data integrity.


When used judiciously, synchronized methods can help create reliable and robust multithreaded Java applications, providing a balance between concurrency and data consistency.