How to stop reading from a scanner if the user inputs a specific keyword?

I need to be able to enter a random number of integers into the console and then enter a special character such as Q when I am finished. However, I am not sure how to validate if the input is an int or not.

The point is for the user to enter x amount of ints, which get sent from client to server and the server returns the result from a simple equation. I plan on sending them one at a time as it can be any amount of ints entered.

I have tried several different ways. I have tried using hasNextInt. I tried nextLine then added each input to an ArrayList then parsed the input.

List<String> list = new ArrayList<>();
String line;

while (!(line = scanner.nextLine()).equals("Q")) {
    list.add(line);
}

list.forEach(s -> os.write(parseInt(s)));

This is another loop I had originally which validates the input fine, but i’m not sure how to exit the loop when done.

while (x < 4) {
    System.out.print("Enter a value: ");

    while (!scanner.hasNextInt()) {    
        System.out.print("Invalid input: Integer Required (Try again):");
    }

    os.write(scanner.nextInt());
    x++;
}

Any help would be appreciated. Thanks

Answer

Here you go:

Scanner scanner = new Scanner(System.in);
List<Integer> list = new ArrayList<Integer>();

while (scanner.hasNext()) {
    String line = scanner.nextLine();

    if (line.equals("Q")) {
        scanner.close();
        break;
    }

    try {
        int val = Integer.parseInt(line);
        list.add(val);
    } catch (NumberFormatException e) {
        System.err.println("Please enter a number or Q to exit.");
    }
}

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Answer