Formatter class doesn't keep data after each time writing on the text file

Question

I am developing a application that write on the text file. application write the data on the file correctly but if I restart the application and write new input it replace the new input to the old one that I write on file perversely, but what i need it is to keep the old input that i wrote before with the new one

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

    public static void main(String[] args)
    {
        openFile();
        addRecords();
        closeFile();
    }

    // open file clients.txt
    public static void openFile()
    {
        try
        {
            output = new Formatter("clients.txt"); // 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();
    }
} // end class CreateTextFile

score 0 · Accepted Answer · answered Sep 22 '20 at 10:45

0

You can use a FileWriter to append to existing file.

Update openFile method as,

// open file clients.txt
public static void openFile()
{
    try
    {
        FileWriter fileWriter = new FileWriter("clients.txt", true);
        output = new Formatter(fileWriter); // 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
    }
}

Note- In FileWriter constructor I have kept append flag as true

answered Sep 22 '20 at 10:45

Vishal

666
1
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this is nice solution but, I am curios to know if it possible to do this functionality with Formatter class.do you think its possible? – pooya Sep 22 '20 at 10:52
No you cannot. If you see https://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#constructor_summary Formatter class's constructor, it allows an implementation of Appendable https://docs.oracle.com/javase/7/docs/api/java/lang/Appendable.html. A FileWriter is an implementation of Appendable. So above solution is the way to use if you want to append to same file. – Vishal Sep 22 '20 at 11:01

Formatter class doesn't keep data after each time writing on the text file

1 Answers1