diff --git a/bin/StringCalculator.class b/bin/StringCalculator.class
index a937b0c..ddf6e4b 100644
Binary files a/bin/StringCalculator.class and b/bin/StringCalculator.class differ
diff --git a/src/StringCalculator.java b/src/StringCalculator.java
index 487916b..364b0ca 100644
--- a/src/StringCalculator.java
+++ b/src/StringCalculator.java
@@ -1,9 +1,54 @@
 
 public class StringCalculator {
-	public int add(String numbersStr) {
+	
+	
+	public int add(String numbersStr) throws StringCalculatorException  {
 		// Returns the sum of the numbers given in numbersStr
+		int sum = 0;
+		int[] numberArray = new int[3];
 		
-		// not yet implemented
-		return 0;
+		if(!numbersStr.isEmpty()) {
+			
+			numberArray = splitInput(numbersStr);
+			for(int i = 0; i < numberArray.length; i++) {
+				if(numberArray[i] >= 0) {
+					testOfValue(numberArray[i]);
+					sum += numberArray[i];
+				} else throw new StringCalculatorException();
+			}
+		}
+		
+
+		return sum;
+	}
+	
+	private int[] splitInput(String numbersToSplit) {
+		String [] numbers;
+		int[] sum = new int[3];
+		numbers = numbersToSplit.split("[,|\n]");
+		if(testOfLength(numbers))		{
+			for(int i = 0; i < numbers.length; i++) {				
+					sum[i] = Integer.parseInt(numbers[i]);				
+			}
+		}
+		
+		return sum; 
 	}
+	
+	private boolean testOfLength(String[] testString) {
+		boolean test;
+		if(testString.length >= 0 && testString.length < 3) {
+			test = true;
+		} else test = false;
+		return test;
+	}
+	
+	private boolean testOfValue(int value) throws StringCalculatorException {
+		boolean test;
+		if(value < 0) {
+			 test = true;
+		} else throw new StringCalculatorException();
+		return test;
+	}
+
 }
diff --git a/src/StringCalculatorException.java b/src/StringCalculatorException.java
index da71147..9f37ce4 100644
--- a/src/StringCalculatorException.java
+++ b/src/StringCalculatorException.java
@@ -1,4 +1,4 @@
 
 public class StringCalculatorException extends Exception {
-
+// I expect that this doesn't need to edited as there was only talk of throwing it
 }