This program uses nested loops to simulate a clock.

Clock.java

/**
   This program uses nested loops to simulate a clock.
*/

public class Clock
{
   public static void main(String[] args)
   {
      //Always show two digits.
      DecimalFormat formatter = new DecimalFormat("00");
      
      // Simulate the clock.
      for (int hours = 1; hours <= 12; hours++)
      {
          for (int minutes = 0; minutes <= 59; minutes++)
          {
             for (int seconds = 0; seconds <= 59; seconds++)
             {
                System.out.println(formatter.format(hours) + ":" + 
                            formatter.format(minutes) + ":" + 
                            formatter.format(seconds)); 
             }
          }
       }
   }
}