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 factorial = 1;
        for(int i=1; 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) {
        String[] acronym = phrase.split(" ");
        String newStr = " ";
        for (int i = 0; i < acronym.length; i++) {
            String s = acronym[i];
            newStr += s.charAt(0);          
        }
        return newStr.replace(" ","").toUpperCase();
    }    

    /**
     * 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[] arr = new char[word.length()];

        for (int i = 0; i < arr.length; i++) {
            if(word.charAt(i) == 'x'){
                arr[i] = 'a';
            } else if (word.charAt(i) == 'y'){
                arr[i] = 'b';
            } else if (word.charAt(i) == 'z'){
                arr[i] = 'c';
            }else {
                arr[i] = (char) (word.charAt(i) + 3);
            }
        }   
           
        
        String result = new String(arr);
        return result;
    
}
}