//  MeanvalueMethod.java  Copyright (c) 2005 Kari Laitinen

//  http://www.naturalprogramming.com

//  2004-10-09  File created.
//  2005-03-27  Last modification.

import java.util.* ;

class MeanvalueMethod
{
   static int ask_numbers_to_array( double[] array_of_numbers )
   {
      Scanner keyboard = new Scanner( System.in ) ;

      int  number_of_given_numbers  =  0  ;

      System.out.print( "   Enter a number: " ) ;

      boolean  keyboard_input_is_numerical  =  true ;

      while ( keyboard_input_is_numerical ==  true  &&
              number_of_given_numbers  <  array_of_numbers.length  )
      {
         try
         {
            double  number_from_keyboard  =  keyboard.nextDouble() ;
            array_of_numbers[ number_of_given_numbers ]
                                         =  number_from_keyboard ;
            number_of_given_numbers ++ ;
            System.out.print(  "   Enter a number: " ) ;
         }
         catch ( Exception  not_numerical_input_exception )
         {
            keyboard_input_is_numerical  =  false ;
         }
      }

      return  number_of_given_numbers ;
   }


   static double calculate_mean_value( double[] array_of_numbers,
                                       int      number_of_numbers_in_array )
   {
      double  calculated_mean_value  =  0 ;
      double  sum_of_numbers         =  0  ;

      for ( int number_index  =  0 ;
                number_index  <  number_of_numbers_in_array ;
                number_index  ++ )
      {
         sum_of_numbers  =  sum_of_numbers  +
                             array_of_numbers[ number_index ] ;
      }

      if ( number_of_numbers_in_array  >  0 )
      {
         calculated_mean_value  = (double) sum_of_numbers /
                                  (double) number_of_numbers_in_array ;
      }

      return  calculated_mean_value  ;
   }

   public static void main( String[] not_in_use )
   {
      double[]  array_of_numbers  =  new  double[ 100 ] ;

      System.out.print( "\n This program calculates the mean value of"
                      + "\n the numbers you enter from the keyboard."
                      + "\n The program stops when you enter a letter.\n\n");

      int  number_of_numbers_read  =
                              ask_numbers_to_array( array_of_numbers ) ;

      double  mean_value  =  calculate_mean_value( array_of_numbers,
                                                   number_of_numbers_read ) ;

      System.out.print( "\n The mean value is: "  +  mean_value  + "\n" ) ;
   }
}