Mechanism that runs my application only at certain times of the day

Question

Hi,
As my title suggests, i'm looking for some code that will allow me to run parts of my application only at a certain time in the day. More specifically, I want the code to run these parts of the application at 5pm only on weekdays.
I've tried various different types of loops to do this, but can't find anyway to do it.
Could somebody suggest a better way of doing it?
Thanks in advance.
Here is some example code of what I tried:
public static void main(String[] args)
     // TIMER
     Calendar cal = new GregorianCalendar();
     // Get the components of the time
     int hour24 = cal.get(Calendar.HOUR_OF_DAY); // 0..23
     int min = cal.get(Calendar.MINUTE); // 0..59
     int today = cal.get(Calendar.DAY_OF_WEEK);
     final int RUNH = 17;
     final int RUNM = 0;
     app start = new app(); //starts the application
     while (!((hour24 == RUNH) && (min == RUNM)) || (today ==1 ) || (today == 6))
          // do nothing
     if((hour24 == RUNH) && (min == RUNM) && ((today != 1) && (today != 7))) // 5:00 on a weekday
          System.out.println ("Update Running " + hour24 + " " + min + " " + today); //runs some sort of update on the application
}

Answer 1

Something like this will work:
long now = System.currentTimeMillis();
GregorianCalendar cal = new GregorianCalendar();
cal.set(Calendar.HOUR,17);
cal.set(Calendar.MINUTE,0);
cal.set(Calendar.SECOND,0);
int day = cal.get(Calendar.DAYOFWEEK);
int yearday = cal.get(Calendar.DAYOFYEAR);
cal.set(Calendar.DAYOFYEAR,yearday + (day == Calendar.FRIDAY)? 3 : 1))
long next = cal.getTime() //don't know... maybe needs another getTime()?
Thread.currentThread.sleep(next-now);