import java.text.DecimalFormat;

/* TimeOfDay.java
** An instance of this class represents an immutable time of day, 
** precise to a minute.  
*/
public class TimeOfDay {

   // class constants
   // ---------------

   private static final int HOUR_CEILING = 24;
   private static final int MINUTE_CEILING = 60;


   // instance variables
   // ------------------

   private final int hour;     // in range [0 .. HOUR_CEILING)
   private final int minute;   // in range [0 .. MINUTE_CEILING)


   // constructor
   // -----------

   /* Sets this TimeOfDay to the specified hour and minute.
   ** Throws an IllegalArgumentException if either parameter is
   ** outside its meaningful range.
   */
   public TimeOfDay(int hr, int min) {
      if (hr < 0  ||  hr >= HOUR_CEILING) {
         throw new IllegalArgumentException("Hour parameter outside legal range.");
      }
      else if (min < 0  ||  min > MINUTE_CEILING) {
         throw new IllegalArgumentException("Minute parameter outside legal range.");
      }
      else {
         hour = hr;
         minute = min;
      }
   }


   // observers
   // ---------

   /* Two obvious "getter" methods.
   */
   public int getHour() { return hour; }
   public int getMinute() { return minute; }

   /* Returns a string describing the time of day represented by this object.
   ** The form of the string is hh:mm, meaning a two-digit hour, a colon, and
   ** a two-digit minute.  Examples: "08:02", "23:15".
   */
   @Override
   public String toString() {
      DecimalFormat df = new DecimalFormat("00");
      return df.format(hour) + ":" + df.format(minute);
   }

}