Synchronized keyword

 Introduction:

In multithreaded Java applications, when multiple threads access shared data concurrently, it can lead to thread interference and race conditions. 

The synchronized keyword is a powerful tool that helps prevent these issues by providing synchronization and ensuring that only one thread can access a synchronized block or method at a time.

Understanding the Synchronized Keyword:

The synchronized keyword in Java is used to control access to critical sections of code, allowing only one thread at a time to execute the synchronized block or method. 

This ensures that shared data modifications are done atomically, avoiding potential data inconsistencies and thread interference.


Using Synchronized Methods:

One way to use the synchronized keyword is by applying it directly to a method. 

When a method is declared as synchronized, it is implicitly synchronized on the object's monitor (intrinsic lock) on which the method is called. 

This means that only one thread can execute the synchronized method at a time.

Example:


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

In this example, the increment() and getCount() methods of the Counter class are declared as synchronized. As a result, concurrent calls to these methods will be synchronized, and only one thread can execute them at a time.


Using Synchronized Blocks:

Alternatively, you can use synchronized blocks to achieve finer-grained synchronization. 

With synchronized blocks, you can specify a specific object (lock) on which the synchronization should occur.

Example:


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

In this example, we introduce a private Object called lock that acts as the monitor for synchronization. The increment() and getCount() methods now use synchronized blocks that are synchronized on the lock object. This allows us to have more fine-grained control over which parts of the code are synchronized.


Benefits of Using the Synchronized Keyword:

Thread Safety: The synchronized keyword ensures that critical sections of code are accessed by only one thread at a time, preventing data corruption and race conditions.

Simplicity: The synchronized keyword provides a straightforward approach to handling concurrency and avoiding complex low-level synchronization.

Implicit Locking: When used with methods, the synchronized keyword automatically locks on the object's monitor, making synchronization seamless.

Considerations:

Overuse: While synchronization helps avoid thread interference, excessive use of synchronized can lead to reduced performance due to contention for locks.

Deadlock: Be cautious when using nested synchronized blocks to avoid potential deadlocks, where threads wait indefinitely for each other to release locks.

Conclusion:

The synchronized keyword is a powerful tool in Java for ensuring thread safety and preventing thread interference and race conditions. 

Whether applied to methods or used with synchronized blocks, the synchronized keyword allows for controlled access to critical sections of code, ensuring that shared data is modified atomically.

 By using synchronization judiciously, you can develop robust and reliable multithreaded Java applications.


Remember to balance the need for thread safety with potential performance overhead. In some cases, higher-level concurrency utilities, such as locks and concurrent data structures, may be more appropriate for specific scenarios.