KYLO-2896: added comment with quartz cron formatting

commons/commons-util/src/test/java/com/thinkbiganalytics/scheduler/quartz/CronExpressionTest.java

@@ -9,9 +9,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *     http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -39,9 +39,21 @@ public class CronExpressionTest {
 
     private static final Logger log = LoggerFactory.getLogger(CronExpressionTest.class);
 
+    /*
+    Cron expressions are comprised of 6 required fields and one optional field separated by white space.
+    The fields respectively are described as follows:
+
+    Field Name	 	Allowed Values	 Allowed Special Characters
+    Seconds	 	0-59	 	 , - * /
+    Minutes	 	0-59	 	 , - * /
+    Hours	 	0-23	 	 , - * /
+    Day-of-month	 1-31	 	 , - * ? / L W
+    Month	 	1-12 or JAN-DEC	 , - * /
+    Day-of-Week	 	1-7 or SUN-SAT	 , - * ? / L #
+    Year (Optional)	empty, 1970-2199 , - * /
+    */
     @Test
     public void testNextFireTimes() {
-
         String cronExpression = "0 0 12 1/1 * ? *"; // every day at 12:00 PM
         try {
             List<Date> dates = CronExpressionUtil.getNextFireTimes(cronExpression, 20);