Question from examlab practice test 3

[geeta vemula]

This is from practice exam 3 of examlab

  public class ThreadClass extends Thread{

     public ThreadClass(int x){
          this.x=x;
     }

     static String s="";
     static volatile int x=0;

     public static void doVIP(){
          s=s+x;
          try{
               Thread.sleep(10);
          }catch(Exception e){
               s=s+x;
          }
     }

     public void run(){
          synchronized(s){
               doVIP();
          }
     }

     public static void doDelay(long g){
          try{Thread.sleep(g);}catch(Exception e){}
     }

     public static void main(String args[]){

          ThreadClass tc1=new ThreadClass(2);
          ThreadClass tc2=new ThreadClass(1);
          ThreadClass tc3=new ThreadClass(0);

          tc1.start(); doDelay(100); System.out.print(s);
          tc2.start(); doDelay(100); System.out.print(s);
          tc3.start(); doDelay(100); System.out.print(s);

     }
}  

here answer is D. will compile succesfully if volatile keyword is removed
I. prints 000000

Here i could not understand if the current code gives compiler error then how come it is printing 000000
even if we remove the voatile keyword then i think it should give output as 221210. please clear my doubt.

thanks,
geeta vemula

[Punit Singh]

I will give you a hint.

  ThreadClass tc3=new ThreadClass(0);  

Concentrate on this line, and do your best to try why? And tell me the answer also.

[geeta vemula]

oh i was so stupid...

First all the instantiation done where x will become 0 in tht line which is same since it is class variable. so printing 000000.

Thanks,
for clearing my doubt..

[Punit Singh]

Excellent

[Fritz Guerilus]

geeta vemula wrote:oh i was so stupid...

First all the instantiation done where x will become 0 in tht line which is same since it is class variable. so printing 000000.

Thanks,
for clearing my doubt..

Thanks for explaination guys.
That line tricked me too.
I also thought the answer should be '000' becuase the print statement is executed three times.
But I manually went through the code step by step and figured out that the static String variable 's' keeps the previous '0's and thus prints out 6-'0's.
Very tricky!
-Thank You