In Java, when can we use synchronized blocks?

Synchronization Block is a piece of code that can be used to perform synchronization on any specific resource of a method. Synchronization block is used to lock any shared resource object, and the scope of the synchronization block is smaller than synchronization method.

Syntax

synchronized(object) {
   // block of code
}

Here, Object is a reference to the object being synchronized. A synchronized block ensures that an object's member methods are called only after the current thread has successfully entered the object's monitor.

Example

class TicketCounter {
   int availableSeats = 2;
   void bookTicket(String name, int numberOfSeats) {
      if((availableSeats >= numberOfSeats) && (numberOfSeats > 0)) {
         System.out.println(name+" : "+ numberOfSeats + " Seats Booking Success");
         availableSeats -= numberOfSeats;
      } else {
         System.out.println(name +" : Seats Not Available");
      }
   }
}
class TicketBookingThread extends Thread {
   TicketCounter tc;
   String name;
   int seats;
   TicketBookingThread(TicketCounter tc, String name, int seats) {
      this.tc = tc;
      this.name = name;
      this.seats = seats;
   }
   public void run() {
<strong>      synchronized(tc) { // synchronized block
</strong>         tc.bookTicket(name, seats);
      }
   }
}
public class SynchronizedBlockTest {
   public static void main(String[] args) {
      TicketCounter tc = new TicketCounter();
      TicketBookingThread t1 = new TicketBookingThread(tc, "Adithya", 2);
      TicketBookingThread t2 = new TicketBookingThread(tc, "Jai", 2);
      t1.start();
      t2.start();
   }
}

Output

Adithya : 2 Seats Booking Success
Jai : Seats Not Available

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