java中已知WEEK_OF_YEAR，确定当前周的周一和周日

Calendar cal = Calendar.getInstance();
cal.set(Calendar.WEEK_OF_YEAR,18);//18为周数
Calendar cal1 = (Calendar)cal.clone();
int dayOfWeek = cal.get(Calendar.DAY_OF_WEEK);
cal.add(Calendar.DATE,cal.getActualMinimum(Calendar.DAY_OF_WEEK)-dayOfWeek);
cal.add(Calendar.DATE, 1);
Date d = cal.getTime();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(sdf.format(d));
cal1.add(Calendar.DATE,cal1.getActualMaximum(Calendar.DAY_OF_WEEK)-dayOfWeek);
cal1.add(Calendar.DATE, 1);
System.out.println(sdf.format(cal1.getTime()));