Update CalculatorResourceTest.java

src/test/java/CalculatorResourceTest.java

@@ -26,7 +26,7 @@ public class CalculatorResourceTest{
     public void testCalculateThreeNumbers(){
         CalculatorResource calculatorResource = new CalculatorResource();
 
-        string expression = "300 + 100 + 500";
+        String expression = "300 + 100 + 500";
         assertEquals("900", calculatorResource.calculate(expression));
 
         expression = "300 - 99 - 1";