All tests passed.

LoopFun.java

@@ -8,7 +8,12 @@ public class LoopFun
        * @return the factorial of the number
        */
       public int factorial(int number){
-          return -1;
+          int answer = 1;
+          for (int i = number; i > 0; i--) {
+              answer = answer * i;
+          
+        }
+        return answer;
       }
 
       /**
@@ -19,7 +24,12 @@ public class LoopFun
        * @return Upper case string of the first letter of each word
        */
       public String acronym(String phrase) {
-          return null;
+          String answer = "";
+          for (String s : phrase.split(" ")) {
+              answer = answer + s.charAt(0);
+            }
+            answer = answer.toUpperCase();
+          return answer;
       }
 
       /**
@@ -35,6 +45,16 @@ public class LoopFun
        * @return the encrypted string by shifting each character by three character
        */
       public String encrypt(String word) {
-          return null;
+          char[] letters = "abcdefghijklmnopqrstuvwxyz".toCharArray();
+          char[] enc = "defghijklmnopqrstuvwxyzabc".toCharArray();
+          String answer = "";
+          int index;
+          
+          for (int i = 0; i < word.length(); i++) {
+            char currentLetter = word.charAt(i);
+            index = (new String(letters).indexOf(currentLetter));
+            answer = answer + (new String(enc).charAt(index));
+        }
+          return answer;
       }
 }

MathUtilities.java

@@ -6,7 +6,8 @@ public class MathUtilities{
    * @return the sum of the two numbers
    */
   public int add(int num1, int num2){
-      return -1;
+      int answer = num1 + num2;
+      return answer;
   }
 
   /**
@@ -16,7 +17,8 @@ public class MathUtilities{
    * @return the sum of the two numbers
    */
   public double add(double num1, double num2){
-      return -1;
+      double answer = num1 + num2;
+      return answer;
   }
 
   /**
@@ -25,7 +27,8 @@ public class MathUtilities{
    * @return the half of the number in double
    */
   public double half(int number) {
-      return -1;
+      double answer = (double) number / 2;
+      return answer;
   }
 
   /**
@@ -34,7 +37,13 @@ public class MathUtilities{
    * @return true if the number is odd, false if it is even
    */
   public boolean isOdd(int number){
-      return false;
+      boolean answer;
+      if (number % 2 == 1) {
+          answer = true;
+        } else {
+            answer = false;
+        }
+      return answer;
   }
 
 
@@ -44,7 +53,8 @@ public class MathUtilities{
    * @return the result of the number multiply by itself
    */
   public int square(int number) {
-      return -1;
+      int answer = number * number;
+      return answer;
   }
 
 }

StringUtilities.java

@@ -1,13 +1,27 @@
 public class StringUtilities {
    public Character getMiddleCharacter(String word){
-       return null;
+       int middleIndex = word.length() / 2;
+       char answer = word.charAt(middleIndex);
+       
+       return answer;
    }
    
    public String removeCharacter(String value, char charToRemove){
-     return null;  
+       String answer = "";
+       for (int i = 0; i < value.length(); i++) {
+           char currentChar = value.charAt(i);
+           if (!(currentChar == charToRemove)) {
+               answer = answer + value.charAt(i);
+            }
+       
+    }
+    return answer;
    }
    
    public String getLastWord(String value) {
-       return null;
+       String answer = value.substring(value.lastIndexOf(" ") + 1);
+       
+       
+       return answer;
    }
 }