public class LoopFun
{

    /**
     * Given a number, return the factorial of that number.
     * For example, given 5, the factorial is 5 x 4 x 3 x 2 x 1 which should return 120.
     * @param number
     * @return the factorial of the number
     */
    public int factorial(int number){
        int factorial = 1;

        for (int i = 2; i <= number; i++) {
            factorial *= i;
        }

        return factorial;
    }

    /**
     * Given a phrase, get the acronym of that phrase. Acronym is the combination of
     * the first character of each word in upper case.
     * For example, given "Ruby on Rails", this method will return "ROR"
     * @param phrase
     * @return Upper case string of the first letter of each word
     */
    public String acronym(String phrase) {
        StringBuilder sbAcronym = new StringBuilder();

        String firstCapital = phrase.substring(0, 1).toUpperCase();
        sbAcronym.append(firstCapital);

        for (int i = 1; i < phrase.length(); i++) {
            if (phrase.charAt(i) == ' ') {
                sbAcronym.append(phrase.charAt(i + 1));
            }
        }

        String Acronym = sbAcronym.toString().toUpperCase();

        return Acronym;
    }

    /**
     * To prevent anyone from reading our messages, we can encrypt it so it will only be readable by its
     * intended audience. This method encrypt the message by shifting the letter by 3 characters. If the character is
     * at the end of the alphabet, it will wraps around.
     * For example:
     *  'a' => 'd'
     *  'w' => 'z'
     *  'x' => 'a'
     *  'y' => 'b'
     * @param word
     * @return the encrypted string by shifting each character by three character
     */
    public String encrypt(String word) {
        // char[] toEncode = word.toCharArray();

        StringBuilder sbEncryption = new StringBuilder(); 

        char arr[] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};

        int k;

        for (int i = 0; i < 26; i++) {
            for (int j = 0; j < word.length(); j++) {
                if (word.charAt(j) == arr[i]){
                    k = i;

                    if (k < 23) {
                        sbEncryption.append(arr[(k + 3)]);
                    }
                    
                    if (k >= 23) {
                        sbEncryption.append(arr[(k - 23)]);
                    } 
                }
            }
        }
        String encryption = sbEncryption.toString();

        return encryption;
    }
}