Turn the time into milliseconds, turn milliseconds into seconds

1, the date and time of the month into milliseconds, calculate the number of milliseconds two time period

Long time1 = 0;
Long time2 = 0;
Long time=0;

SimpleDateFormat sdf=new SimpleDateFormat ("Yyyy-mm-dd HH:mm:ss");

Calendar cal = Calendar.getinstance ();

Cal.settime ("time period 1");
time1 = Cal.gettimeinmillis ();
Cal.settime ("time period 2");
Time2 = Cal.gettimeinmillis (); Calculated in milliseconds
time=time2-time1;

2. Convert milliseconds to seconds

             SimpleDateFormat formatter = new SimpleDateFormat ("HH:MM: SS ");//Initialize the formatter transformation format.      
             Formatter.settimezone ( Timezone.gettimezone ("gmt+00:00"));
             String HMS = Formatter.format (time); //time as the number of milliseconds to convert , the long type