fix:添加注释

src/main/java/com/study/design/service/OrderService.java

@@ -30,7 +30,7 @@ public class OrderService {
     private StateMachinePersister<OrderState, OrderStateChangeAction, Order> stateMachinePersister;
 
     /**
-     * 模拟一个存储
+     * 模拟一个存储DB
      */
     private final List<Object> orders = new ArrayList<>();
 
@@ -119,7 +119,7 @@ public class OrderService {
 
 
     /**
-     * 状态变更
+     * 状态变更,消息通知
      *
      * @param message
      * @param order