fix bug

hutool-cron/src/main/java/cn/hutool/cron/Scheduler.java

@@ -397,7 +397,7 @@ public class Scheduler implements Serializable {
 		try {
 			checkStarted();
 
-			if(null != this.threadExecutor){
+			if(null == this.threadExecutor){
 				// 无界线程池，确保每一个需要执行的线程都可以及时运行，同时复用已有线程避免线程重复创建
 				this.threadExecutor = ExecutorBuilder.create().useSynchronousQueue().setThreadFactory(//
 						ThreadFactoryBuilder.create().setNamePrefix("hutool-cron-").setDaemon(this.daemon).build()//

hutool-cron/src/test/java/cn/hutool/cron/demo/CronTest.java

@@ -38,7 +38,7 @@ public class CronTest {
 		ThreadUtil.waitForDie();
 		CronUtil.stop();
 	}
-	
+
 	@Test
 	@Ignore
 	public void cronWithListenerTest() {