CharacterCheck

public class CahracterCheck {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in); // Create a Scanner object
        String input = ""; // Initialize input string
        // do-while loop
        do {
            System.out.print("Enter a character: "); // ask for a character
            input = scanner.next(); // Read user input
            String charType = getCharacterType(input); // get the character type
            System.out.println("Character is: " + charType); // Output user input
            System.out.println("---------------------"); // new line
        } while (!isEnd(input)); // loop runs until "done" is encountered
        // encountered
        scanner.close();
        System.out.println("===== THANK YOU =====");
    }

    // function to check the character type
    private static String getCharacterType(String input) {
        if (input.length() > 1) {
            if (isEnd(input)) {
                return "TERMINATION"; // if the input is "done" return the type "TERMINATION"
            } else {
                return "INVALID"; // return invalid as the input contains more than one charcacter and is not
                                    // "done"
            }
        } else {
            char c = input.charAt(0); // getting the character at 0 position of input
            // ASCII Values
            // 0-9 >> 48-57
            // A-Z >> 65-90
            // a-z >> 97-122
            if (c >= 48 && c <= 57) {
                return "NUMBER"; // from 48 till 57 the character is number
            } else if (c >= 65 && c <= 90) {
                return "CAPITAL LETTER";// from 65 till 90 the character is capital letter
            } else if (c >= 97 && c <= 122) {
                return "SMALL LETTER";// from 97 till 122 the character is small letter
            } else {
                return "SPECIAL SYMBOL";// else the character is special symbol

            }
        }
    }

    // check if the program is to end
    private static boolean isEnd(String input) {
        if (input.length() == 4) {
            char[] c = input.toCharArray(); // input string converted to char array for simplicity
            if ((c[0] == 'D' || c[0] == 'd') && (c[1] == 'O' || c[1] == 'o') && (c[2] == 'N' || c[2] == 'n')
                    && (c[3] == 'E' || c[3] == 'e')) {
                return true; // if DONE is encountered in any combination eg; DoNe, done, DONE, donE, etc the
            } // program ends
            else {
                return false; // else the program doesn't end as the input is not "DONE"
            }
        } else {
            return false; // if input length is not 4 the program continues as "done" contains exactly 4
        } // letters
    }
}