CreateTextFile.java

// Fig. 15.3: CreateTextFile.java
// Writing data to a sequential text file with class Formatter.
import java.io.FileNotFoundException;     
import java.lang.SecurityException;       
import java.util.Formatter;               
import java.util.FormatterClosedException;
import java.util.NoSuchElementException;  
import java.util.Scanner;                 

public class CreateTextFile
{
   private static Formatter output; // outputs text to a file       

   public static void main(String[] args)
   {
      String filename = "clients.txt";
      if (args.length>0) filename = args[0];
      openFile(filename);
      addRecords();
      closeFile();
   } 

   // open file clients.txt
   public static void openFile(String filename)
   {
      try
      {
         output = new Formatter(filename); // open the file
      }
      catch (SecurityException securityException)
      {
         System.err.println("Write permission denied. Terminating.");
         System.exit(1); // terminate the program
      } 
      catch (FileNotFoundException fileNotFoundException)
      {
         System.err.println("Error opening file. Terminating.");
         System.exit(1); // terminate the program
      } 
   } 

   // add records to file
   public static void addRecords()
   {
      Scanner input = new Scanner(System.in);
      System.out.printf("%s%n%s%n? ", 
         "Enter account number, first name, last name and balance.",
         "Enter end-of-file indicator to end input.");

      while (input.hasNext()) // loop until end-of-file indicator
      {
         try
         {
            // output new record to file; assumes valid input
            output.format("%d %s %s %.2f%n", input.nextInt(),
               input.next(), input.next(), input.nextDouble());                             
         } 
         catch (FormatterClosedException formatterClosedException)
         {
            System.err.println("Error writing to file. Terminating.");
            break;
         } 
         catch (NoSuchElementException elementException)
         {
            System.err.println("Invalid input. Please try again.");
            input.nextLine(); // discard input so user can try again
         } 

         System.out.print("? ");
      }
   }

   // close file
   public static void closeFile()
   {
      if (output != null)
         output.close();
   } 
}