Question

I have a very simple loop that waits for a number (int) and as long as that number is not exitOption it does not leave the loop, however I get an unexpected error, and I don’t know what’s causing it.

Edit

Adding another snippet so you can compile

public static void main(String[] args) throws   FileNotFoundException,
                                                SecurityException,
                                                IOException,
                                                ClassNotFoundException {


    while (controller.selectOptionMM());

/Edit

public boolean selectOptionMM() throws  SecurityException, 
                                        FileNotFoundException, 
                                        IOException {

    int cmd = ui.getExitOption();

    ui.mainMenu();
    cmd = utils.readInteger(">>> "); // this is my problem, right here
                                     // code in next snippet 
    while (cmd <1 || cmd > ui.getExitOption()) {
        System.out.println("Invalid command!");
        cmd = utils.readInteger(">>> ");
    }

    switch (cmd) {
    case 1: 
    case 2: 
    case 3: 
    case 4: this.repository.close();
            return true;
    case 5: return false;
    }

    return false;
}

Here is what fails:

public int readInteger(String cmdPrompt) {
    int cmd = 0;
    Scanner input = new Scanner(System.in);

    System.out.printf(cmdPrompt);
    try {
        if (input.hasNextInt()) 
            cmd = input.nextInt(); // first time it works
            // Second time it does not allow me to input anything
                            // catches InputMissmatchException, does not print message
                            // for said catch
                            // infinitely prints "Invalid command" from previous snippet

    } catch (InputMismatchException ime) {
        System.out.println("InputMismatchException: " + ime);
    } catch (NoSuchElementException nsee) {
        System.out.println("NoSuchElementException: " + nsee);
    } catch (IllegalStateException ise) {

    } finally {
        input.close(); // not sure if I should test with if (input != null) THEN close
    }


    return cmd;
}

First time I pass trough, it reads the number no problem. Now if the number is not 5 (in this case exitOption), it passes again trough readInteger(String cmdPrompt) except this time it jumps to catch (InputMismatchException ime) (debug) except it does not print that message and just jumps to Error, input must be number and Invalid command.

Is something stuck in my input buffer, can I flush it, why is it (input buffer) stuck (with random data)???

I’ll try debugging again and see what’s stuck in my input buffer, if I can figure out how to see that.

Answer 1

The problem is in the call to input.close() – this causes the underlying input stream to be closed. When the input stream being closed is System.in, bad things happen (namely, you can’t read from stdin any more). You should be OK just eliminating this line.