import java.io.*;

// this class demonstrate some of the popular recursive ideas
public class recursive
{
   public static void main(String[] argv)
   {
       System.out.println(" ---- dish wash : ----");
       dishWash(5);  // there are five dishes to wash
       System.out.println(" ---- factorial : ----");
       System.out.println(" factorial 6 should be 720");
       System.out.println(" factorial 6 is equal to : " + factorial(6));
       System.out.println(" ---- summation : ----");
       System.out.println(" summation 6 should be 21");
       System.out.println(" summation 6 is equal to : " + sum(6));
       System.out.println(" ---- exponentiation : ----");
       System.out.println(" power (3,4) should be 81");
       System.out.println(" power(3,4) is equal to : " + power(3,4));
       System.out.println(" test finished ...");
   } // main

   static void dishWash(int count)
   {
       if (count == 0)
       {
	   System.out.println(" dish wash completes.");
       }
       else
       {
	   // wash one dish
	   System.out.println(" There are " + count + " more dishes to wash ...");
           System.out.println(" Mmm, wash one dish ");
/***
	   System.out.print(" this is the " + count);
	   switch (count)
	   {
	       case 1 : System.out.print(" -st ");
	                break;
	       case 2 : System.out.print(" -nd ");
		        break;
	       case 3 : System.out.print(" -rd ");
                        break;
	      default : System.out.print(" -th ");
	   }
	   System.out.println(" one");
***/
           dishWash(count - 1);  // recursive call
       } // if-then-else
   } // dishWash

   static int factorial(int x)
   {
       if (x == 0)
	   return 1;
       else
	   return x * factorial(x - 1);
   }  // factorial

   static int sum(int x)
   {
       if (x == 0)
	   return 0;
       else
	   return x + sum(x - 1);
   } // sum

   static int power(int x, int p)
   {
       if (p == 0)
	   return 1;
       else
	   return x * power(x, p - 1);
   } // power
}