Question

How to generate a random string of 5 characters without importing random library?

Answer 1

public class Main {

    public static void main(String[] args) {

        String characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        StringBuilder result = new StringBuilder();

        for(int i = 0; i < 5; i++) {

            int index = (int)(Math.random() * characters.length());
            result.append(characters.charAt(index));
        }

        System.out.println(result.toString());
    }
}

Comments

Still uses  int index = (int)(Math.random() * characters.length());

Answer 2

import os
import string
import secrets # secrets module is generally available without separate installation

def generate_random_string(length):
    # Define the possible characters
    characters = string.ascii_uppercase + string.digits
    result = ''
    # Read random bytes from the OS
    random_bytes = os.urandom(length * 4) # Read more bytes to ensure enough randomness

    for i in range(length):
        # Use a byte to select a character index securely
        # % len(characters) ensures the index is within the valid range
        index = random_bytes[i] % len(characters)
        result += characters[index]
        
    return result

# Example usage
random_string = generate_random_string(5)
print(random_string)