Question

I have a scanner reading from a text file. When it gets to a certain line in the file, I want to be able to call a method that uses the Scanner as a parameter in its current state – as in, I want the scanner to be passed (along with the file used) at exactly what line it’s on.

public static void createEntry(File list, int mediaTypeNum, String mediaType) throws FileNotFoundException {
    Scanner mediaReader = new Scanner(list);
    int occurrence = mediaTypeNum;
    int scannerCounter = 0;
    String match;
    String title = "";
    String director = "";
    while (mediaReader.hasNext() && scannerCounter < occurrence) {
        match = mediaReader.nextLine();
        if (match.equalsIgnoreCase(mediaType)) {
            scannerCounter++;
            if (scannerCounter == occurrence) {
                // based on type, create the media object
                // createMediaObject(list, mediaReader, mediaType)
                title = mediaReader.nextLine();
                director = mediaReader.nextLine();
            }
        }
    }

createMediaObject() will have a switch case, and based on the case, the Scanner will read some following lines until there’s a blank line. For each media type, the number of lines differ.

Thank you in advance!

Answer 1

Of course, it is in fact true to any object in Java. No implicit copies of objects are created at any point.*

What you have to be careful about is that Scanner has a “sequential” state and if you’re passing it around a lot, it’s very easy to lose track of what state it is in. Especially if conditional processing is performed, where different execution paths might end up leaving it at different positions.

A good approach to this is to always document in the method Javadoc what state the Scanner is expected to be in and what state it’s left at the end.

*There’s a big caveat to that statement: multithreading. But it would be highly off topic to discuss that here in detail.