Uppercase to lowercase conversion without using any library function in Java

Java code for uppercase to lowercase conversion

// Uppercase to lowercase conversion without using 
// any library function in Java

public class Main {
    static String UpperToLower(String s) {
        String result = "";
        char ch = ' ';
        for (int i = 0; i < s.length(); i++) {
            
            //check valid alphabet and it is in Uppercase
            if (s.charAt(i) >= 'A' && s.charAt(i) <= 'Z') {
                ch = (char)(s.charAt(i) + 32);
            }
            //else keep the same alphabet or any character
            else {
                ch = (char)(s.charAt(i));
            }
            
            result += ch; // concatenation, append c to result
        }
        return result;
    }

    public static void main(String[] args) {
        System.out.println(UpperToLower("IncludeHelp.com"));
        System.out.println(UpperToLower("www.example.com"));
        System.out.println(UpperToLower("123ABCD@9081"));
        System.out.println(UpperToLower("OKAY@123"));        
    }
}

Output

includehelp.com
www.example.com
123abcd@9081
okay@123