Synchronization

synchronized void methodName() {
  // critical section
}

class Counter {

  int count = 0;

  synchronized void increment() {
    count++;
  }

}

class MyThread extends Thread {

  Counter c;

  MyThread(Counter c) {
    this.c = c;
  }

  public void run() {
    for (int i = 1; i <= 1000; i++) {
      c.increment();
    }
  }

}

public class Main {

  public static void main(String[] args) throws Exception {

    Counter c = new Counter();

    MyThread t1 = new MyThread(c);
    MyThread t2 = new MyThread(c);

    t1.start();
    t2.start();

    t1.join();
    t2.join();

    System.out.println("Final Count: " + c.count);

  }

}

// Output:
// Final Count: 2000

• 1 Controls access to shared resources.
• 2 Ensures thread safety.
• 3 Prevents race conditions.
• 4 Works with locks in JVM.

• 1 Method synchronization.
• 2 Block synchronization.
• 3 Static synchronization.
• 4 Object-level locking.

• 1 To avoid data inconsistency.
• 2 To prevent race conditions.
• 3 To ensure thread safety.
• 4 To manage shared resources.

• 1 Deadlock – threads waiting forever.
• 2 Starvation – thread never gets access.
• 3 Performance overhead.
• 4 Reduced concurrency.