Calendar cal = Calendar.getInstance();
SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");
cal.setTime(format.parse("20061225"));
int week = cal.get(Calendar.WEEK_OF_YEAR);
2006-12-25:
Calendar cal = new GregorianCalendar(Locale.CHINA);
Date date = new GregorianCalendar(2006, 11, 25, 11, 40).getTime();
cal.setTime(date);
cal.get(Calendar.WEEK_OF_YEAR);