QuizWeek1/LoopFun.java

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 sum = 1;

        for(int i = 1; i <= number; i++){
            sum *= i;
        }
        return sum;
    }

    /**
     * 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) {
        String[] phraseAcro = phrase.split(" ");
        StringBuilder sb = new StringBuilder();

        for(int i=0; i < phraseAcro.length; i++){
            sb.append(phraseAcro[i].charAt(0));
        }

        String x = sb.toString().toUpperCase();

        return x;
    }

    /**
     * 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) {
        String shifted = "";
        for (int i = 0; i < word.length(); i++)
        {
            if (isLetter(word.charAt(i)))
            {
                shifted = shifted + shift(word.charAt(i), shift);
            }
            else
            {
                shifted = shifted + original.charAt(i);
            }
        }

        return shifted;
    }
}