import java.util.Scanner;

/* Java application that produces a Fahrenheit-to-Celsius conversion table.
** The user provides as input (via the keyboard) the floor and ceiling
** Fahrenheit temperatures and the "delta" (the amount by which each line's
** Fahrenheit temperature exceeds that of the previous line).
** (This version improves upon the previous one by using System.out.printf()
** to format the temperature readings so that they line up nicely in the
** two columns (with the decimal points directly above/below each other in
** the same column).)
**
** Author: R. McCloskey
** Date: March 2015
*/

public class FahToCel5 {

   // Create a new Scanner object that can read input from the keyboard.
   // By being declared here (outside any method), this variable becomes
   // "global", meaning that its scope is the entire class.
   private static Scanner keyboard = new Scanner(System.in);

   public static void main(String[] args) {

      // Declare the input variables
      double fahFloor;    // first Fah. temp. in the table
      double fahDelta;    // increase in Fah. temp. from one row to next
      double fahCeil;     // upper bound on Fah. temp.'s in the table

      // For each input, prompt the user and read it.
      fahFloor = getDoubleResponse("Enter Fahrenheit floor temperature: ");
      fahDelta = getDoubleResponse("Enter Fahrenheit delta: ");
      fahCeil = getDoubleResponse("Enter Fahrenheit ceiling: ");

      // Produce the table.
      printTable(fahFloor, fahDelta, fahCeil);
   }


   /* Displays the specified prompt, reads the user's response (using
   ** the global Scanner object, keyboard), converts it to a value of
   ** type double, and returns that value to the caller.
   */
   private static double getDoubleResponse(String prompt)
   {
      System.out.print(prompt);      // Display the prompt.
      return keyboard.nextDouble();  // Read response and return it.
   }

   /* Prints the Fahrenheit-to-Celsius conversion table, where the first
   ** row's Fah. temp, the increase in Fah. temp from one row to the next,
   ** and the ceiling Fah. temp. are provided via the parameters.
   */
   private static void printTable(double fLow, double fDelta, double fHigh)
   {
      // Print column headings.
      System.out.printf("%15s %9s\n","Fahrenheit", "Celsius");
      System.out.printf("%15s %10s\n","----------", "---------");

      // Alternative to above printing of column headings:
      //System.out.println("     Fahrenheit   Celsius");
      //System.out.println("     ----------  ---------");


      // Produce the body of the table.  Each loop iteration produces
      // a single row, which includes a row number, a Fahrenheit temp.,
      // and the equivalent Celsius temp.
      int rowNum = 1;
      for (double fah = fLow; fah <= fHigh; fah = fah + fDelta)
      {
         double celTemp = fahToCel(fah);

         // Display the row number in a field of width 3, followed by a period
         // and a few spaces, the Fahrenheit temperature (fah) in a field of
         // width 7 with 2 digits after the decimal point, followed by 'F', 
         // followed by a few spaces, followed by the equivalent Celsius
         // temperature (celTemp) in a field of width 8 with 3 digits after
         // the decimal point, followed by 'C', and use the newline character
         // ('\n') to advance to the next line.
         System.out.printf("%3d.  %7.2fF  %8.3fC\n", rowNum, fah, celTemp);

         rowNum = rowNum + 1;  // increment the row number
      }
   }

   /* Returns the Celsius equivalent of the given Fahrenheit temperature (f).
   */
   private static double fahToCel(double f) {
      return (5.0 / 9.0) * (f - 32);
   }

}