MOre fixes 2 calc

src/main/java/resources/CalculatorResource.java

@@ -52,7 +52,7 @@ public class CalculatorResource {
      */
     public int sum(String expression){
         String[] split = expression.split("[+]");
-        int length = len(split);
+        int length = split.length();
         int sum = 0;
 
         for(int i = 0; i<length; i++){
@@ -69,7 +69,7 @@ public class CalculatorResource {
      */
     public int subtraction(String expression){
         String[] split = expression.split("[-]");
-        int length = len(split);
+        int length = split.length();
         int result = 0;
         
         for(int i = 0; i<length; i++){
@@ -81,7 +81,7 @@ public class CalculatorResource {
 
     public int multiplication(String expression){
         String[] split = expression.split("[*]");
-        int length = len(split);
+        int length = split.length();
         int result = 0;
 
         for(int i = 0; i<length; i++){
@@ -93,7 +93,7 @@ public class CalculatorResource {
 
     public int division(String expression){
         String[] split = expression.split("[/]");
-        int length = len(split);
+        int length = split.length();
         int result = 0;
 
         for(int i = 0; i<length; i++){