android - why countdown counter with thread show wrong value? -

i don't know why count down counter shows random number @ end?
mean shows 60:15, 60:07, on way

min=sec=0; new thread(new runnable() {     @override     public void run() {         while (min < 60  && flagtime) {             try {                 thread.sleep(1);                 g.handler.post(new runnable() {                     @override                     public void run() {                         string presec="";                         string premin="";                         if (sec < 59) {                             sec += 1;                         }                         if (sec < 10) {                             presec = "0";                         }                          if (min < 10) {                             premin = "0";                         }                         score =premin + min + ":"                                 + presec + sec;                         txt[elementnumber + 1].settext(score);                     }                 });             } catch (exception e) {                 e.printstacktrace();             }         }     } }).start(); 

please tell me why works weird?

timing in oses not precise, unless use framework or tools designed task. can work thread.sleep reasonable uncertainty. "reasonable" , "precise" timing, depends on problem trying solve.

in threads, sleep(1000) not mean thread sleep 1 second, thread sleep less or more every time run app. why random results.

this has many things else consider priority of thread. better way count down use other ways provided android:

countdowntimer

timer

you may check on google , find many examples how use them.

those more reliable , more precise.

hope helps.