/**
 * This program reads numbers from a file.  It computes the sum and the average
 * of the numbers that it reads.  The file should contain nothing but numbers of type
 * double; if this is not the case, the output will be the sum and average of however 
 * many numbers were successfully read from the file.  The name of the file will
 * be input by the user.
 */
public class ReadNumbersFromFile {
   
   public static void main(String[] args) {
            
      while (true) {
         String fileName;  // The name of the file, to be input by the user.
         TextIO.put("Enter the name of the file: ");
         fileName = TextIO.getln();
         try {
            TextIO.readFile( fileName );  // Try to open the file for input.
            break;  // If that succeeds, break out of the loop.
         }
         catch ( IllegalArgumentException e ) {
            TextIO.putln("Can't read from the file \"" + fileName + "\".");
            TextIO.putln("Please try again.\n");
         }
      }
      
      // At this point, TextIO is reading from the file.
      
      double number;  // A number read from the data file.
      double sum;     // The sum of all the numbers read so far.
      int count;      // The number of numbers that were read.
      
      sum = 0;
      count = 0;
      
      try {
         while (true) { // Loop ends when an exception occurs.
             number = TextIO.getDouble();
             count++;  // This is skipped when the exception occurs
             sum += number;
         }
      }
      catch ( IllegalArgumentException e ) {
         // We expect this to occur when the end-of-file is encountered.
         // We don't consider this to be an error, so there is nothing to do
         // in this catch clause.  We just proceed with the rest of the program.
      }
      
      // At this point, we've read the entire file, so we can print the results.
      
      TextIO.putln();
      TextIO.putln("Number of data values read: " + count);
      TextIO.putln("The sum of the data values: " + sum);
      if ( count == 0 )
         TextIO.putln("Can't compute an average of 0 values.");
      else
         TextIO.putln("The average of the values:  " + (sum/count));
      
   }

}