import java.util.Scanner;
import java.io.*;

/**
  DistanceFile
  CS 111A Programming Lab 7 solution
  by Tony Gaddis for Starting Out with Java
  modified by Craig Persiko
*/

public class DistanceFile
{
  /* input a number from the user, using prompt as an inline prompt,
  ensuring the number is >= num.  The name of this data is name. */
  private static double getNumber(String prompt, int min, String name)
  {
    Scanner keyboard = new Scanner(System.in);
    double num;

    System.out.print(prompt);
    num = keyboard.nextDouble();

    // Validate the speed.
    while (num < min)
    {
      System.out.print("Enter " + min + " or greater for " + name + ": ");
      num = keyboard.nextDouble();
    }
    return num;
  }

   public static void main(String[] args) throws IOException
   {
      double speed;     // The vehicle's speed
      int maxHours,     // Max number of hours traveled
          period;       // To count time periods

      // Get the speed.
      speed = getNumber("Enter the vehicle's speed: ", 0, "speed");

      // Get the number of hours.
      maxHours = (int)getNumber("Enter the number of hours the " +
                                "vehicle was in motion: ", 1, "hours");

      // Create the objects necessary to perform file output.
      FileWriter fw = new FileWriter("DistanceReport.txt");
      PrintWriter outFile = new PrintWriter(fw);

      // Write the table header.
      outFile.printf ("Hour             Distance Traveled\n");
      outFile.println("----------------------------------");

      // Write the table of distances.
      period = 1;
      while (period <= maxHours)
      {
         // Display the distance for this period.
         outFile.printf("%3d %,24.1f\n",period, period * speed);

         // Increment period.
         period++;
      }

      // Close the file.
      outFile.close();
      System.out.println("Report written to DistanceReport.txt.");
   }
}

/* Sample Output:

-bash-3.2$ java DistanceFile
Enter the vehicle's speed: 120
Enter the number of hours the vehicle was in motion: 11
Report written to DistanceReport.txt.
-bash-3.2$ cat DistanceReport.txt
Hour             Distance Traveled
----------------------------------
  1                    120.0
  2                    240.0
  3                    360.0
  4                    480.0
  5                    600.0
  6                    720.0
  7                    840.0
  8                    960.0
  9                  1,080.0
 10                  1,200.0
 11                  1,320.0
-bash-3.2$ java DistanceFile
Enter the vehicle's speed: -2
Enter 0 or greater for speed: 3.25
Enter the number of hours the vehicle was in motion: 0
Enter 1 or greater for hours: 4
Report written to DistanceReport.txt.
-bash-3.2$ cat DistanceReport.txt
Hour             Distance Traveled
----------------------------------
  1                      3.3
  2                      6.5
  3                      9.8
  4                     13.0
-bash-3.2$
*/