How can I do the input loop that exits the program?

“Enter a word or press ‘Q’ to quit” but I don’t know how to do it. It seems confusing to me a little bit.

This is my first time coding in Java and I’m still learning.

public class RemSpecialChar {
    public static void main(String[] args) {
        try (Scanner scan = new Scanner(System.in)) {

            String stringArray = "";
            
            do {
                System.out.print("Enter a word or 'Q' to quit: ");
                String str = scan.nextLine();
                for (int i = 0; i < str.length(); i++) {
                    if (str.charAt(i) > 64 && str.charAt(i) <= 122) { //returns true if both conditions returns true    
                        //adding characters into empty string
                        stringArray = stringArray + str.charAt(i);
                    }
                    System.out.print("Input string without special characters: " + stringArray); //string results
                }
            }
            while (stringArray != "q" || stringArray != "Q");
        }
    }
}


THIS IS THE SAMPLE OUTPUT:
Enter a word or 'Q' to quit: Black?204123,.Scoop (input)
Input string without special characters: BlackScoop (output)
Enter a word or 'Q' to quit: q (input)
(end program)


terminal output:
Enter a word or 'Q' to quit: q
Enter a word or 'Q' to quit: q
Enter a word or 'Q' to quit: q
Enter a word or 'Q' to quit: q
Enter a word or 'Q' to quit: q
Enter a word or 'Q' to quit: q
Enter a word or 'Q' to quit: q
Enter a word or 'Q' to quit:

Answer

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        try (Scanner scan = new Scanner(System.in)) {
            while (true) {
                String inputdata = scan.nextLine();

                if (inputdata.length() == 1 && (inputdata.charAt(0) == 'Q' || inputdata.charAt(0) == 'q')) {
                    break;
                }

                String stringArray = "";
                for (int i = 0; i < inputdata.length(); i++) {
                    if (inputdata.charAt(i) > 64 && inputdata.charAt(i) <= 122) { // returns true if both conditions
                                                                                  // returns true
                        // adding characters into empty string
                        stringArray = stringArray + inputdata.charAt(i);
                    }

                }
                System.out.print("Input string without special characters: " + stringArray);

            }

        }
    }
}