Interview Question for Java Engineer at Nextlabs:

public class Test{
    public final static int NUMTHREADS = 1000;
    public final static int NUMLOOP = 1000;
    public static int num = 0;

    static class Mythread extends Thread{
        @Override
        public void run(){
            for (int i = 0; i < NUMLOOP; i++){
                add();
            }
        }
        private synchronized static void add(){
            ++num;
        }
    }

    public static void main(String argv[]){
        Mythread threads[] = new Mythread[NUMTHREADS];
        for (int i = 0; i < NUMTHREADS; ++i){
            threads[i] = new Mythread();
            threads[i].start();
        }
        try{
            for (int i = 0; i < NUMTHREADS; ++i){
                threads[i].join();
            }
        }catch (InterruptedException e){}
        System.out.println("Num: " + num);
    }
}