public class Demo extends Thread {

    private static int count;

    public static void increment() {
        count++;
    }

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            increment();
        }
    }

    // -------------------------------------------------------------

    public static void main(String args[]) {
        System.out.println("The counter starts at " + count);

        // Create, but do not start, 2 threads.
        Thread thread1 = new Demo();
        Thread thread2 = new Demo();

        // Start the 2 threads.
        thread1.start();
        thread2.start();

        // Now 3 threads are running: main, thread1, thread2.

        // Wait until both threads have finished.
        // Note: join can through an exception
        try {
            thread1.join();
            thread2.join();
        } catch (InterruptedException e) {
            System.out.println("uh oh, unexpected thread failure");
            System.exit(1);
        }

        // Now thread1 and thread2 have terminated, so it's safe to
        // access count.
        System.out.println("The counter is now " + count);        
    }
}