Updated JavaDoc to note that a couple of parameters may be updated

src/main/java/edu/unl/cse/csce361/calculator/Calculator.java

@@ -87,8 +87,10 @@ public class Calculator {
      *
      * @param type         the type of token received from the user
      * @param token        the token received from the user
-     * @param stack        an array representing the calculator's stack
-     * @param stackPointer the value indicating the top of the stack
+     * @param stack        an array representing the calculator's stack; this parameter may be updated when the
+     *                     method returns
+     * @param stackPointer the value indicating the top of the stack; this parameter may be updated when the method
+     *                     returns
      * @return the message to be displayed to the user, or {@code Null} if no message is to be displayed
      */
     String calculate(int type, char[] token, double[] stack, AtomicInteger stackPointer) {