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 result = 1;
          for(int i=1; i<=number; i++){
              result = result * i;
              System.out.println();
            }
          return result;
      }

      /**
       * 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) {
          int firstSpaceIndex = phrase.indexOf(" ");
          int lastSpaceIndex = phrase.lastIndexOf(" ");
          phrase = phrase.toUpperCase();
          String result = phrase.substring(0,1);
          while (lastSpaceIndex > firstSpaceIndex && firstSpaceIndex != -1) {
              result = result + phrase.substring(firstSpaceIndex+1, firstSpaceIndex+2);
              phrase = phrase.substring(0,firstSpaceIndex) + phrase.substring(firstSpaceIndex+1);
              firstSpaceIndex = phrase.indexOf(" ");
            }
          return result;
      }

      /**
       * 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 alphabet = "abcdefghijklmnopqrstuvwxyzabcde";
          String codedWord = "";
          for (int i=0; i<word.length(); i++) {
            int alphaIndex = alphabet.indexOf(word.charAt(i));
              codedWord += String.valueOf(alphabet.charAt(alphaIndex+3));
            }
          return codedWord;
      }
}