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

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.");
	}
}

Do it as follows:

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		List<Integer> list = new ArrayList<Integer>();
		String input = "";
		while (true) {
			System.out.print("Enter an integer (Q to quit): ");
			input = in.nextLine();
			if (input.equalsIgnoreCase("Q")) {
				break;
			}
			if (!input.matches("\\d+")) {
				System.out.println("This is an invalid entry. Please try again");
			} else {
				list.add(Integer.parseInt(input));
			}
		}
		System.out.println(list);
	}
}

A sample run:

Enter an integer (Q to quit): a
This is an invalid entry. Please try again
Enter an integer (Q to quit): 10
Enter an integer (Q to quit): b
This is an invalid entry. Please try again
Enter an integer (Q to quit): 20
Enter an integer (Q to quit): 10.5
This is an invalid entry. Please try again
Enter an integer (Q to quit): 30
Enter an integer (Q to quit): q
[10, 20, 30]

Notes:

1. while(true) creates an infinite loop.
2. \\d+ allows only digits i.e. only an integer number.
3. break causes the loop to break.