Synchronized method does not work as expected

Question

I have a variable which is shared by two threads. The two threads will do some operations on it. I don\'t know why the result of sharedVar is different every time I execute

Answer 1

Join the thread immediately after start method. From this thread-1 will start and go to dead state after that thread-2 will start and go to dead state. So it will print your expected output always.

Change the code as shown below:-

public class Main{

    public static int sharedVar = 0;

    public static void main(String[] args)

        {
            MyThread mt1 = new MyThread();
            MyThread mt2 = new MyThread();

            try

                {
                    mt1.start();
                    mt1.join();
                    mt2.start();
                    mt2.join();
                }

            catch (InterruptedException e1)

                {
                    e1.printStackTrace();
                }

            System.out.println(sharedVar);

        }
}

class MyThread extends Thread
{
    private int times = 1000000;

    private synchronized void addOne()
        {
            for (int i = 0; i < times; ++i)
                {
                    Main.sharedVar++;
                }
        }

    @Override
    public void run()
        {
            addOne();
        }
}