在try子句中引发异常

Question

I am doing a project that requires the use of File I/O. The relevant code is as follows:

Scanner testscn = new Scanner(input).useDelimiter("\n");
    testscn.forEachRemaining((scan) -> {
        String[] line = scan.split("-");

        try {
            File img = new File(line[0]);
            if (!img.exists()) throw new FileNotFoundException();
            test.put(img, line[1].split(","));
        } catch (FileNotFoundException e) {
            logger.warn("File path " + line[0] + " could not be resolved. Skipping.");
        }
    });
    testscn.close();

Is it a bad practice to throw the FileNotFoundException simply to put my execution onto another path?

Answer 1

What you are doing will "work". However, most Java programmers would probably agree that this is an example of using exceptions to implement "normal" flow control. It is simpler to write it like this:

Scanner testscn = new Scanner(input).useDelimiter("\n");
testscn.forEachRemaining((scan) -> {
    String[] line = scan.split("-");

    File img = new File(line[0]);
    if (img.exists()) {
        test.put(img, line[1].split(","));
    } else {
        logger.warn("File path " + line[0] + ": Skipping.");
    }
});
testscn.close();

And that should be rewritten like this to avoid a potential resource leak:

try (Scanner testscn = new Scanner(input).useDelimiter("\n")) {
    testscn.forEachRemaining((scan) -> {
        String[] line = scan.split("-");

        File img = new File(line[0]);
        if (img.exists()) {
            test.put(img, line[1].split(","));
        } else {
            logger.warn("File path " + line[0] + ": Skipping.");
        }
    });
}