public class SynchronizedMethod {
    /**
     * Print 10 numbers without synchronization. Sleep randomly
     * between calls to println.
     */
    private static class AdderSync implements Runnable {
        private int n = 0;

        public synchronized void run() {
            for(int i = 0; i < 1000; i++) {
                n++;
            }
        }
        public synchronized int getN() {
            return n;
        }
    }
   
    /**
     * Print 10 numbers *with* synchronization. Sleep randomly between
     * calls to println.
     */
    private static class AdderNoSync implements Runnable {
        private int n = 0;

        public void run() {
            for(int i = 0; i < 1000; i++) {
                n++;
            }
        }
        public int getN() {
            return n;
        }
    }

    public static void main(String[] args) {
        Thread t1, t2, t3, t4;

        // Run 4 threads with AdderSync
        System.out.println("* AdderSync");
        AdderSync adder1 = new AdderSync();
        t1 = new Thread(adder1);
        t2 = new Thread(adder1);
        t3 = new Thread(adder1);
        t4 = new Thread(adder1);
        t1.start();
        t2.start();
        t3.start();
        t4.start();
        try {
            t1.join();
            t2.join();
            t3.join();
            t4.join();
        } catch(InterruptedException e) {
            System.err.println("Thread Interrupted");
        }
        System.out.println("n = " + adder1.getN());

        // Run 4 thrads with AdderNoSync
        System.out.println("* AdderNoSync");
        AdderNoSync adder2 = new AdderNoSync();
        t1 = new Thread(adder2);
        t2 = new Thread(adder2);
        t3 = new Thread(adder2);
        t4 = new Thread(adder2);
        t1.start();
        t2.start();
        t3.start();
        t4.start();
        try {
            t1.join();
            t2.join();
            t3.join();
            t4.join();
        } catch(InterruptedException e) {
            System.err.println("Thread Interrupted");
        }
        System.out.println("n = " + adder2.getN());
    }
}