Example of Thread Synchronization - Synchronized Method

Printing.java

package ThreadSynchronizing;
/**
 * A synchronized method, once having taken up a task, cannot be accessed by another threads until it completes the task.
 * When one thread is executing a synchronized method for an object, all other threads that invoke synchronized methods for the same object block (suspend execution) until the first thread is done with the object.
 * References:
 * https://docs.oracle.com/javase/tutorial/essential/concurrency/sync.html
 * Programming in JAVA2 Dr. K. Somasundaram
 * */
class Printing
{
    synchronized void printNumbers(int n){
        System.out.println("Start");
        for (int i = n; i>0 ; i--) {
            if(i==n/2){
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println(i);
        }
        System.out.println("End");
    }
}
class ThreadServe implements Runnable
{
    int n;
    Printing pt;
    Thread th;
    ThreadServe(Printing pt, int x)
    {
        n=x;
        this.pt = pt;
        th = new Thread(this);
        th.start();
    }
    @Override
    public void run() {
        pt.printNumbers(n);
    }
}
  class ThreadSyncDemo
{
    public static void main(String[] args) {
        Printing p = new Printing();
        ThreadServe ts1 = new ThreadServe(p, 16);
        ThreadServe ts2 = new ThreadServe(p, 8);
        ThreadServe ts3 = new ThreadServe(p, 10);
    }
}

Sample Output

Start
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
End
Start
8
7
6
5
4
3
2
1
End
Start
10
9
8
7
6
5
4
3
2
1
End