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 making better use of
** methods.  In particular, a method that produces the table is introduced,
** as is one that prompts the user for an input of type double and returns
** the user's response.)
**
** Author: R. McCloskey
** Date: March 2015
*/

public class FahToCel4 {

   // 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 starting Fahrenheit temp: ");
      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.println("Fahrenheit    Celsius");
      System.out.println("----------   ---------");

      // Produce the body of the table.  Each loop iteration produces
      // a single row.
      for (double fah = fLow; fah <= fHigh; fah = fah + fDelta)
      {
         double celTemp = fahToCel(fah);
         System.out.println(fah + "F       " + celTemp + "C");
      }
   }

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

}