diff --git a/bin/StringCalculator.class b/bin/StringCalculator.class
index a937b0c..b934107 100644
Binary files a/bin/StringCalculator.class and b/bin/StringCalculator.class differ
diff --git a/bin/StringCalculatorException.class b/bin/StringCalculatorException.class
index 4bd9894..096b146 100644
Binary files a/bin/StringCalculatorException.class and b/bin/StringCalculatorException.class differ
diff --git a/bin/StringCalculatorTest.class b/bin/StringCalculatorTest.class
index d44b83f..44258ae 100644
Binary files a/bin/StringCalculatorTest.class and b/bin/StringCalculatorTest.class differ
diff --git a/src/StringCalculator.java b/src/StringCalculator.java
index 487916b..618ac83 100644
--- a/src/StringCalculator.java
+++ b/src/StringCalculator.java
@@ -1,9 +1,183 @@
+import java.util.StringTokenizer;
 
-public class StringCalculator {
-	public int add(String numbersStr) {
-		// Returns the sum of the numbers given in numbersStr
+public class StringCalculator{
+	
+	public int int1;
+	public int int2;
+	
+	public int add(String numbersStr) throws StringCalculatorException{
+		
+		int int1 = 0;
+		int int2 = 0;
+		int result = -1;
+		String[] token = new String[2];
+		
+		if(countLines(numbersStr) > 1) {
+			
+			result = addlines(numbersStr);
+			
+		}
+		
+		else {
+		
+			if(countTokens(numbersStr) == 0) {
+					
+				
+				result = 0;
+				
+			}
+				
+			else if(countTokens(numbersStr) == 1) {
+				
+			
+				token = getToken(numbersStr);
+				int1 = getNumber(token[0]);
+				result = int1;
+				
+			}
+			
+			
+			else if(countTokens(numbersStr) == 2) {
+				
+				token = getToken(numbersStr);
+				int1 = getNumber(token[0]);
+				int2 = getNumber(token[1]);
+				result = sum(int1, int2);
+				
+			}
+				
+			else{
+				
+				result = addMoreThanTwoNumbers(numbersStr);
+				
+			}
+			
+		}
+	
+		return result;
+		
+	}
+	
+	public int addMoreThanTwoNumbers(String s) throws StringCalculatorException{
+		
+		int numTokens = countTokens(s);
+		
+		String[] token = getToken(s);
+		
+		int number = 0;
+		
+		int sum = 0;
+		
+		for(int i = 0; i < numTokens; i++) {
+			
+			number = getNumber(token[i]);
+			
+			sum += number;
+			
+		}
+		
+		return sum;
+		
+	}
+	
+	public int addlines(String s) throws StringCalculatorException{
+		
+		String[] line = getLine(s);
+		int number = 0;
+		int sum = 0;
+		int numToken = 0;
+		
+		for(int i = 0; i < line.length; i++) {
+			
+			numToken = countTokens(line[i]);
+			
+			String[] token = new String[numToken];
+			
+			token = getToken(line[i]);
+			
+			for(int j = 0; j < numToken; j++) {
+				
+				number = getNumber(token[j]);
+				sum += number;
+				
+			}
+			
+		}
+		
+		return sum;
+		
+	}
+	
+	public int countTokens(String s) {
+		
+		StringTokenizer st = new StringTokenizer(s, ",");
+		
+		int tokenNum = 0;
+		
+		while(st.hasMoreTokens()) {
+			
+			tokenNum ++;
+			st.nextToken();
+			
+		}
+		
+		return tokenNum;
+		
+	}
+	
+	public int countLines(String s) {
+		
+		StringTokenizer st = new StringTokenizer(s, "\n");
+		
+		int lineNum = 0;
+		
+		while(st.hasMoreTokens()) {
+			
+			lineNum ++;
+			st.nextToken();
+			
+		}
+		
+		return lineNum;
+		
+	}
+	
+	public String[] getLine(String s) {
+		
+		String[] st = s.split("\n");
+		
+		return st;
+		
+	}
+	
+	public String[] getToken(String s) {
+		
+		String[] st = s.split(",");
+	
+		return st;
+	}
+	
+	public int getNumber(String s)
+			  throws StringCalculatorException
+	  {  
+		
+		int number = 0;
+		number = Integer.parseInt(s);
+	    if(number < 0)
+	    	throw new StringCalculatorException();
+	    else
+	    {
+	    	return number;
+	    }
+	    
+	    
+	    
+	  }
+	
+	public int sum(int int1, int int2) {
+		
+		return int1 + int2;
 		
-		// not yet implemented
-		return 0;
 	}
+	
 }
diff --git a/src/StringCalculatorException.java b/src/StringCalculatorException.java
index da71147..8e6b853 100644
--- a/src/StringCalculatorException.java
+++ b/src/StringCalculatorException.java
@@ -1,4 +1,8 @@
 
 public class StringCalculatorException extends Exception {
 
+	public StringCalculatorException(){
+		System.out.println("Invalid number");
+	  }  
+	
 }
diff --git a/tests/StringCalculatorTest.java b/tests/StringCalculatorTest.java
index 4ec9afe..3221eff 100644
--- a/tests/StringCalculatorTest.java
+++ b/tests/StringCalculatorTest.java
@@ -3,10 +3,174 @@
 import org.junit.Test;
 
 public class StringCalculatorTest {
+	
+	//Test countToken method
+	//-------------------------------------------------------------------
+	
+	@Test
+	public void countToken_0Number() {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(0, sc.countTokens(""));
+	}
+	
+	@Test
+	public void countToken_1Number() {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(1, sc.countTokens("2,"));
+	}
+	
+	@Test
+	public void countToken_2Number() {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(2, sc.countTokens("2, 3"));
+	}
+	
+	@Test
+	public void countToken_3Number() {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(3, sc.countTokens("2, 3, 4"));
+	}
+	
+	//Test getToken method
+	//-------------------------------------------------------------------
+	
+	@Test
+	public void getToken_1Number() {
+		StringCalculator sc = new StringCalculator();
+		String st[] = new String[1];
+		st = sc.getToken("2,");
+		assertEquals("2", st[0]);
+	}
+	
+	@Test
+	public void getToken_2Number() {
+		StringCalculator sc = new StringCalculator();
+		String st[] = new String[2];
+		st = sc.getToken("2,3");
+		assertEquals("3", st[1]);
+	}
+	
+	//Test getNumber method
+	//-------------------------------------------------------------------
+
+	@Test
+	public void getNumber_1() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(1, sc.getNumber("1"));
+	}
+	
+	//Test getNumber method
+	//-------------------------------------------------------------------
 
 	@Test
-	public void test() {
-		fail("Not yet implemented");
+	public void sum_1_2() {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(3, sc.sum(1, 2));
 	}
+	
+	//Test add method
+	//-------------------------------------------------------------------
 
+	@Test
+	public void add_None() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(0, sc.add(""));
+	}
+	
+	@Test
+	public void add_1() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(3, sc.add("3"));
+	}
+	
+	@Test
+	public void add_1_2() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(3, sc.add("1,2"));
+	}
+	
+	//Test addMoreThanTwoNumbers method
+	//-------------------------------------------------------------------
+	
+	@Test
+	public void add_1_2_3_4() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(10, sc.addMoreThanTwoNumbers("1,2,3,4"));
+	}
+	
+	@Test
+	public void add_1_2_3_4_5_6_7_8() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(36, sc.addMoreThanTwoNumbers("1,2,3,4,5,6,7,8"));
+	}
+	
+	//Test lineNum method
+	//-------------------------------------------------------------------
+		
+	@Test
+	public void countLine_1() {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(1, sc.countLines("1,2,3,4"));
+	}
+
+	@Test
+	public void countLine_2() {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(2, sc.countLines("1,2\n3,4"));
+	}
+	
+	@Test
+	public void countLine_3() {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(3, sc.countLines("1\n2\n3,4"));
+	}
+	
+	//Test getLine method
+	//-------------------------------------------------------------------
+	
+	@Test
+	public void getLine_1() {
+		StringCalculator sc = new StringCalculator();
+		String[] line = sc.getLine("1,2\n3");
+		assertEquals("1,2", line[0]);
+	}
+	
+	@Test
+	public void getLine_2() {
+		StringCalculator sc = new StringCalculator();
+		String[] line = sc.getLine("1,2\n3");
+		assertEquals("3", line[1]);
+	}
+	
+	@Test
+	public void getLine_3() {
+		StringCalculator sc = new StringCalculator();
+		String[] line = sc.getLine("1,2\n3,4,5\n6,7,8");
+		assertEquals("6,7,8", line[2]);
+	}
+	
+	//Test addLine method
+	//-------------------------------------------------------------------
+	
+	@Test
+	public void addLine_2_lines() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(6, sc.addlines("1,2\n3"));
+	}
+	
+	@Test
+	public void addLine_3_lines() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		assertEquals(21, sc.addlines("1,2\n3,4\n5,6"));
+	}
+	
+	//Test exceptions
+	//-------------------------------------------------------------------
+	
+	@Test(expected = StringCalculatorException.class)
+	public void add_exception_negative_input() throws StringCalculatorException {
+		StringCalculator sc = new StringCalculator();
+		sc.addlines("-1");
+	}
+	
 }