snippet(JAVA).sanitizeInput

#RAW the menu

         boolean running = true;
            while (running) {
                displayMainMenu();
                String choice = scanner.nextLine();
                log("User selected option: " + choice);
                
                switch (choice) {

#RAW: from a menu in https://github.com/kvnbbg/feenysh

                switch (choice) {
                    case "1":
                        interactWithStoryQuestions();
                        break;
                    case "2":
                        if (mathCaptchaChallenge()) {
                            accessGrantedContent();
                        } else {
                            System.out.println(RED + "\nToo many failed attempts. Please try again later." + RESET);
                        }
                        break;
                    case "3":
                        displayContactInfo();
                        break;
                    case "4":
                        System.out.println(GREEN + "\nExiting Feenysh. Thank you for visiting!" + RESET);
                        running = false;
                        break;
                    default:
                        System.out.println(RED + "\nInvalid choice. Please try again." + RESET);
                }

To make the input validation simpler and more robust against non-integer inputs, you can use a loop with hasNextInt() from the Scanner class. Here’s a cleaner approach:

Scanner scanner = new Scanner(System.in);
int choice = 0;

// Get valid integer input
while (true) {
    System.out.print("Enter your choice (1-4): ");
    if (scanner.hasNextInt()) {
        choice = scanner.nextInt();
        scanner.nextLine(); // consume the newline
        if (choice >= 1 && choice <= 4) {
            break;
        } else {
            System.out.println(RED + "\nPlease enter a number between 1 and 4." + RESET);
        }
    } else {
        System.out.println(RED + "\nInvalid input. Please enter a number." + RESET);
        scanner.nextLine(); // clear the invalid input
    }
}

// Now use the validated integer in your switch
switch (choice) {
    case 1:
        interactWithStoryQuestions();
        break;
    case 2:
        if (mathCaptchaChallenge()) {
            accessGrantedContent();
        } else {
            System.out.println(RED + "\nToo many failed attempts. Please try again later." + RESET);
        }
        break;
    case 3:
        displayContactInfo();
        break;
    case 4:
        System.out.println(GREEN + "\nExiting Feenysh. Thank you for visiting!" + RESET);
        running = false;
        break;
}

more simple is:

List<String> validChoices = List.of("1", "2", "3", "4");
String choice = scanner.nextLine();

if (!validChoices.contains(choice)) {
    System.out.println(RED + "\nInvalid choice. Please enter 1-4." + RESET);
    continue;
}

switch (choice) {
    // ... same cases as before ...
}

yes or no

Scanner scanner = new Scanner(System.in);
String userInput;

while (true) {
    System.out.print("Do you want to continue? (yes/no): ");
    userInput = scanner.nextLine().trim().toLowerCase(); // Convert to lowercase for case-insensitivity

    if (userInput.equals("yes") || userInput.equals("no")) {
        break; // Valid input, exit loop
    } else {
        System.out.println(RED + "Invalid input. Please enter 'yes' or 'no'." + RESET);
    }
}

// Now process the valid input
if (userInput.equals("yes")) {
    System.out.println(GREEN + "Continuing..." + RESET);
    // Your logic for "yes"
} else {
    System.out.println(RED + "Exiting..." + RESET);
    // Your logic for "no"
}

To sanitize text inputs (allowing only letters, spaces, and basic punctuation) while rejecting numbers and special symbols, you can use regex (regular expressions) or a simple character-checking loop.

---

Method 1: Using Regex (Best for Strict Control)

This method checks if the input contains only letters, spaces, apostrophes, hyphens, and basic punctuation (adjust as needed).

import java.util.Scanner;

public class InputSanitizer {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String userInput;

        while (true) {
            System.out.print("Enter your text (no numbers/symbols): ");
            userInput = scanner.nextLine().trim();

            // Regex: Allows letters, spaces, apostrophes, hyphens, and basic punctuation
            if (userInput.matches("^[\\p{L} ,.!?'-]+$")) {
                break; // Valid input
            } else {
                System.out.println("Invalid input! Only letters, spaces, and basic punctuation allowed.");
            }
        }

        System.out.println("Valid input: " + userInput);
        scanner.close();
    }
}

Explanation of Regex:

• ^ and $ → Match the entire string.
• \\p{L} → Matches any Unicode letter (supports multiple languages).
• ,.!?'- → Allows spaces, commas, periods, exclamation marks, question marks, apostrophes, and hyphens.
• + → Ensures at least one character is present.

---

Method 2: Manual Character Check (More Control)

If you want strict ASCII-only letters (A-Z, a-z) and reject everything else:

public static boolean isTextOnly(String input) {
    for (char c : input.toCharArray()) {
        if (!Character.isLetter(c) && c != ' ' && c != '\'' && c != '-') {
            return false; // Reject if not a letter, space, apostrophe, or hyphen
        }
    }
    return !input.isEmpty(); // Also ensure input is not blank
}

// Usage:
while (true) {
    System.out.print("Enter your name: ");
    String name = scanner.nextLine().trim();

    if (isTextOnly(name)) {
        System.out.println("Valid name: " + name);
        break;
    } else {
        System.out.println("Invalid! Only letters, spaces, apostrophes, and hyphens allowed.");
    }
}

---

Method 3: Allow Only Letters (No Punctuation)

If you want strictly alphabetic input (no numbers, symbols, or spaces):

if (userInput.matches("^[a-zA-Z]+$")) {
    System.out.println("Valid alphabetic input.");
} else {
    System.out.println("Only letters A-Z allowed!");
}

---

Method	Best For	Example Allowed Input
Regex (\\p{L})	Multilingual support	"José O'Connor"
Manual Check	Strict ASCII letters	"John Doe"
Letters Only ([a-zA-Z])	Strict alphabetic (no spaces/symbols)	"Hello"

Let’s gooooooooo! 🚀