Thread: Reading from a txt file and loop trouble

The code:

// This program will read in from a file a series of numbers in degrees
// Celsius, convert them to degree Fahrenheit and print out a table of 
// those values.  The file input is handled using the command line's 
// redirection mechanism.
 
import java.util.Scanner;
 
public class Lab4b
{
   public static void main(String[] args)
   {
      // Declare variables
      Scanner scan = new Scanner(System.in);
 
      double degreeCelsius;
      double degreeFahrenheit;
 
      // Print to the screen the header of the output table
      // as seen in the sample run below.
      // There are two lines in the header.
      // Make sure it has the right spacing to line up with the table.
      System.out.println("Celsius    | Fahrenheit");
      System.out.println("-----------+-----------");
 
      // Write your loop here
      // We want to loop until there are no more inputs to be read. 
 
      while( scan.hasNext())
      {
         // Check to see if the input is a double.
         // If a double read in and store in degreeCelsius.
         // If not a double print an error message and quit.
         if (scan.hasNextDouble())
			degreeCelsius = scan.nextDouble();
 
		 else
		 {
			System.out.println("Error in input");
			System.out.println("Programming is terminating...");
		        System.exit(0);
		 }
 
 
         // Convert input degrees Celsius to degrees Fahrenheit
         // and store in degreeFahrenheit.
         // f = c * (9.0/5.0) + 32.0
 
         degreeFahrenheit = degreeCelsius * (9.0/5.0) + 32.0;
 
         // Display to the screen the output as shown in the 
         // sample run below.  Use System.out.printf.  Make sure
         // that everything lines up properly.
         System.out.printf("       degreeCelsius%d|       degreeFahrenheit%d%n");
 
      } // End of loop
   } // End of main method
} // End class

I cant figure out what I am doing wrong in the loop.

When I try and compile I get an initialization error

C:\Users\Mitchell\My Documents\cs1113\Labs>javac Lab4b.java
Lab4b.java:52: error: variable degreeCelsius might not have been initialized
degreeFahrenheit = degreeCelsius * (9.0/5.0) + 32.0;

So.. I set degreeCelsius = 0;
Then it compiles but when I run the command java Lab4b < lab4data.txt

C:\Users\Mitchell\My Documents\cs1113\Labs>java Lab4b < lab4data.txt
Celsius | Fahrenheit
-----------+-----------
degreeCelsiusException in thread "main" java.util.MissingFormatArgumentEx
ception: Format specifier 'd'
at java.util.Formatter.format(Formatter.java:2487)
at java.io.PrintStream.format(PrintStream.java:970)
at java.io.PrintStream.printf(PrintStream.java:871)
at Lab4b.main(Lab4b.java:57)

So either I am having trouble with the loop or the printf statement
Any hints/tips on those would be great



Here is the txt file it has to read in:
5.5
15.2
25.4
35.8
45.1
55.9
65.3
75.7
85.6
95.0

And here is the print format is has to look like:

command in cmd: java Lab4b < lab4data.txt

Celsius | Fahrenheit
-----------+-----------
5.50| 41.90
15.20| 59.36
25.40| 77.72
35.80| 96.44
45.10| 113.18
55.90| 132.62
65.30| 149.54
75.70| 168.26
85.60| 186.08
95.00| 203.00

^^^^The lines have to match up^^^^

Where does the posted code read from a file?

Look at the API doc for the printf() method. It has a link to the Format String syntax in the Formatter class.