Updating an old line inside a text file

Question

Okay, so i have an issue trying to update a line or sentence in a text file.

The way my program works is this: If a user enters a question the program searches the text file for that exact question(lets say is n). The answer to the question would be on the following line(n + 1). My issue is trying to update the following line(n + 1) to some new line entered by the user.

I keep getting a Exception in thread "main" java.util.NoSuchElementException: No line found when i try to update the line in the text file. my removedata() is where i am trying to update the line of text.

Here is my code

public static void removedata(String s) throws IOException {

    File f = new File("data.txt");
    File f1 = new File("data2.txt");
    BufferedReader input = new BufferedReader(new InputStreamReader(
            System.in));
    BufferedReader br = new BufferedReader(new FileReader(f));
    PrintWriter pr = new PrintWriter(f1);
    String line;

    while ((line = br.readLine()) != null) {
        if (line.contains(s)) {

            System.out.println("Enter new Text :");
            String newText = input.readLine();
            line = newText;
            System.out.println("Thank you, Have a good Day!");

        }

        pr.println(line);
    }
    br.close();
    pr.close();
    input.close();
    Files.move(f1.toPath(), f.toPath(), StandardCopyOption.REPLACE_EXISTING);

}

public static void parseFile(String s) throws IOException {

    File file = new File("data.txt");
    Scanner scanner = new Scanner(file);
    Scanner forget = new Scanner(System.in);
    while (scanner.hasNextLine()) {
        final String lineFromFile = scanner.nextLine();
        if (lineFromFile.contains(s)) {
            System.out.println(scanner.nextLine());

            System.out
                    .println(" Would you like to update this information ? ");
            String yellow = forget.nextLine();
            if (yellow.equals("yes")) {
                removedata(scanner.nextLine()); // NoSuchElementException
                                                // error
            } else if (yellow.equals("no")) {

                System.out.println("Have a good day");
                // break;
            }

        }
    }
}

public static void getinput() throws IOException {

    Scanner scanner = new Scanner(System.in);
    String input = null;
    /* End Initialization */
    System.out.println("Welcome ");
    System.out.println("What would you like to know?");

    System.out.print("> ");
    input = scanner.nextLine().toLowerCase();
    parseFile(input);
}

public static void main(String args[]) throws ParseException, IOException {
    /* Initialization */
    getinput();

}

My text file is :

           what is the textbook name?
           the textbook name is Java
           how is the major?
           the major is difficult
           how much did the shoes cost?
           the shoes cost ten dollars 

Can someone help me solve this issue?

Answer 1

Change the code in the if block in parsefile to

String temp = scanner.nextLine();
System.out.println(temp);

System.out
        .println(" Would you like to update this information ? ");
String yellow = forget.nextLine();
if (yellow.equals("yes")) {
    removedata(temp); // NoSuchElementException
                                    // error
} else if (yellow.equals("no")) {

    System.out.println("Have a good day");
    // break;
}

for an explanation why this works, look at Nick L.s answer.

Answer 2

The problem is here:

while (scanner.hasNextLine()) {                         //(1)
        final String lineFromFile = scanner.nextLine(); //(2)
        if (lineFromFile.contains(s)) {                 //(3)
            System.out.println(scanner.nextLine());     //(4)
        //....
            String yellow = forget.nextLine();          //(5)
            if (yellow.equals("yes")) {
                removedata(scanner.nextLine());         //(6)
            }
        }
//....
}

First of all, you are correctly iterating the scanner lines checking whether there is a line (1). Now, you are getting the first line of the scanner on (2), but if the condition (3) succeeds, you are retrieving the next line again at (4) inside System.out.println(....). Same thing applies to (5) and (6) accordingly.

Now, imagine that you have reached the end of file at (2) and the condition at (3) succeeds. You will receive an exception of no such line, as you logically have. The same can happen at (5) and (6).

Each call of the nextLine(), will get the next line of the file opened on the stream.

I suggest that you do one readline inside the loop, then apply the received string when needed.