Question

I have a file that I put some numbers into but then I decided I wanted to label the numbers with a name for each one, like so:

A = 1 2 3
B = 3 4 5
C = 6 7 8

This caused an exception to be thrown. I want to know how I can workaround this so the scanner ‘ignores’ all but the numbers unless I tell it otherwise.

Can anyone help?

EDIT:

Also, I already know what is causing the exception. I am using next.Double(); to pick out the numbers in the file.

public static void readFile() throws IOException, FileNotFoundException {

    String fileName = "vectors.txt";


    // Reference the file using the the BufferedReader object
    BufferedReader input = new BufferedReader(new FileReader(fileName));    

    //scanner to scan through file 
    Scanner token = new Scanner(input);

    double fileX = token.nextDouble();
    double fileY = token.nextDouble();
    double fileZ = token.nextDouble();

    vecA = new Vector3D(fileX,fileY,fileZ);

    fileX = token.nextDouble();
    fileY= token.nextDouble();
    fileZ = token.nextDouble();

    vecB = new Vector3D(fileX, fileY, fileZ);

    fileX = token.nextDouble();
    fileY= token.nextDouble();
    fileZ = token.nextDouble();

    //initialize vecC using double values from third line of file
    vecC = new Vector3D(fileX, fileY, fileZ);


    //close file 
    input.close();


}

Answer 1

You cannot make the scanner ignore input automatically, but you can write code to skip input yourself until you see that a double is available:

while (!scanner.hasNextDouble()) {
    scanner.next();
}
double d = scanner.nextDouble();

If you need to put this code in multiple places, you can wrap it in a function:

private static double skipAndGetDouble(Scanner scanner) {
    while (scanner.hasNext() && !scanner.hasNextDouble()) {
        scanner.next();
    }
    return scanner.hasNextDouble() ? scanner.nextDouble() : Double.NaN;
}