Use a more informative message when there is a missing command descri…

…ption

src/main/java/command/Command.java

@@ -37,7 +37,7 @@ public static int getTaskNumberFromMessage(String message) throws InvalidTaskNum
     public static void validateDescriptionNotEmpty(CommandTypeEnum commandType, String description)
             throws MissingCommandDescriptionException {
         if (description.isEmpty()) {
-            throw new MissingCommandDescriptionException(commandType.toString());
+            throw new MissingCommandDescriptionException(commandType);
         }
     }
 

src/main/java/exception/MissingCommandDescriptionException.java

@@ -1,5 +1,7 @@
 package exception;
 
+import type.CommandTypeEnum;
+
 /**
  * Encapsulates an exception when a user inputs a command with an empty description,
  * but the command requires a description.
@@ -10,10 +12,11 @@ public class MissingCommandDescriptionException extends DukeException {
      *
      * @param commandType Command type.
      */
-    public MissingCommandDescriptionException(String commandType) {
+    public MissingCommandDescriptionException(CommandTypeEnum commandType) {
         super(String.format(
-                "The description of a %s command cannot be empty",
-                commandType
+                "The description of a %s command cannot be empty. Please enter the command in this format: %s",
+                commandType.toString(),
+                commandType.getFormat()
         ));
     }
 }