Part Three Completed and Commented

src/AssessmentPartThree.java

@@ -17,20 +17,24 @@ public class AssessmentPartThree {
 		 // Lower case characters remain lower case, upper case remain upper case
 		 // Any other characters are returned unchanged
 		 
+		 //Checks whether the character is a digit or a whitespace. If so then the digit/whitespace is returned as there is no encrypted character for these.
 		 if (Character.isDigit(theChar) || Character.isWhitespace(theChar)) {
 			 return theChar;
 		 }
 		 
+		 //Initialises a character array with all the alphabetical characters.
 		 char[] letters = {'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'};
 		 
-		 if (Character.toUpperCase(theChar) == theChar) {
-			 
+		 if (Character.toUpperCase(theChar) == theChar) { //Tests if the current character is upper case.
+			 //If so then the letters array is converted to uppercase characters.
 			 for (int i=0; i<letters.length;i++) {
 				 letters[i] = Character.toUpperCase(letters[i]);
 			 }
 			 
 		 }
 		 
+		 //Searches the letters array, finding the index of the current character in the alphabet.
+		 //If no character is found, the index is left as -1; indicating that the character cannot be encrypted using this algorithm.
 		 int index = -1;
 		 for (int i=0; i<letters.length; i++) {
 			 if (theChar == letters[i]) {
@@ -38,25 +42,29 @@ public class AssessmentPartThree {
 			 }
 		 }
 		 
+		 //Checks if the character can be ciphered.
 		 if (index != -1) {
 			 
+			 /*If the index of the ciphered character is less or equal to the length of the letters array
+			 and it is greater or equal to zero, then the index of the ciphered character is simply the sum of the index and theOffset.
+			 */
 			 if (((index+theOffset) <= letters.length) && (((index + theOffset) >= 0))) {
 				 index = index + theOffset;
 			 }
-			 else if ((index + theOffset) < 0) {
-				 index = letters.length + (index + theOffset);
+			 else if ((index + theOffset) < 0) { //Otherwise if the index of ciphered character is less than zero, the index of the ciphered character is 
+				 index = letters.length + index + theOffset; //the sum of the length of the alphabet array, the index and theOffset.
 			 }
-			 else {
-				 index = (index + theOffset) - letters.length;
+			 else { //Otherwise if the calculated index of the ciphered character is greater than length of the alphabet array, the index of the ciphered character is
+				 index = (index + theOffset) - letters.length; //subtracting the length of the alphabet  from the sum of the index and theOffset. 
 			 }
 			 
 		 }
 		 
-		 if (index == -1) {
-			 return theChar;
+		 if (index == -1) { //If the ciphered character cannot be calculated.
+			 return theChar; //Return the original character.
 		 }
-		 else {
-			return letters[index]; 
+		 else { //If the ciphered character can be calculated. 
+			return letters[index];  //Return the character at the new index.
 		 }
 	 }
 	 
@@ -65,12 +73,12 @@ public class AssessmentPartThree {
 		 // 06 - encryptedMessage
 		 // Complete this method so that it uses encryptedCharacter to 
 		 // return the encrypted version of theMessage using theOffset
-		 String message = "";
+		 String message = ""; //Initialises variable for the cipher text.
 		 
-		 for (int i=0; i<theMessage.length();i++) {		 		 
-			 char current = theMessage.charAt(i);
-			 char newChar = enryptedCharacter(current, theOffset);
-			 message = message + newChar;		 
+		 for (int i=0; i<theMessage.length();i++) {	//Iterates through the plaintext string.		 
+			 char current = theMessage.charAt(i); //Gets the character at the current index.
+			 char newChar = enryptedCharacter(current, theOffset); //Calls the encryptedCharacter function to calculate and return the encrypted character.
+			 message = message + newChar; //Adds the new encrypted character to the cipher text string.	 
 		 }
 		 
 		 return message;