import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Main {
    public static void main(String[] args) {
        CountMonitor mon = new CountMonitor();
        Runnable task = new MyTask(mon);
        Thread worker = new Thread(task);
        Thread worker2 = new Thread(task);
        worker.start();
        worker2.start();
    }
}
class MyTask implements Runnable {
    private final int MAX_COUNT = 10000;
    private CountMonitor mon;

    public MyTask(CountMonitor mon) {
        this.mon = mon;
    }
    
    public void run() {
        System.out.println("Starting! Shared counter: " + mon.getCounter());
        for (int i = 0; i < MAX_COUNT; i++) {
            mon.increment();
        }
        System.out.println("Done! Shared counter: " + mon.getCounter());
    }
}
class CountMonitor {
    private final Lock lock = new ReentrantLock();
    private int sharedCounter = 0;

    public void increment() {
        lock.lock();
        try {
            sharedCounter = sharedCounter + 1;
        } finally {
            lock.unlock();
        }
    }
    public int getCounter() {return sharedCounter;}
}