--- /dev/null	2018-06-17 23:18:20.806999507 +0800
+++ new/test/jdk/jfr/api/flightrecorder/TestRegisterUnregisterEvent.java	2019-01-29 11:01:06.920014227 +0800
@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.jfr.api.flightrecorder;
+
+import static jdk.testlibrary.Asserts.assertEquals;
+
+import jdk.jfr.Event;
+import jdk.jfr.EventType;
+import jdk.jfr.FlightRecorder;
+
+/*
+ * @test
+ * @key jfr
+ * @library /lib/testlibrary
+ * @run main/othervm jdk.jfr.api.flightrecorder.TestRegisterUnregisterEvent
+ */
+public class TestRegisterUnregisterEvent {
+
+    public static void main(String[] args) throws Throwable {
+        // Register before Flight Recorder is started
+        FlightRecorder.register(MyEvent.class);
+        // Repeat
+        FlightRecorder.register(MyEvent.class);
+
+        FlightRecorder recorder = FlightRecorder.getFlightRecorder();
+        int count = 0;
+        for (EventType et : recorder.getEventTypes()) {
+            if (et.getName().equals(MyEvent.class.getName())) {
+                count++;
+            }
+        }
+        assertEquals(1, count);
+
+        FlightRecorder.unregister(MyEvent.class);
+
+        count = 0;
+        for (EventType et : recorder.getEventTypes()) {
+            if (et.getName().equals(MyEvent.class.getName())) {
+                count++;
+            }
+        }
+        assertEquals(0, count);
+
+        FlightRecorder.register(MyEvent.class);
+
+        count = 0;
+        for (EventType et : recorder.getEventTypes()) {
+            if (et.getName().equals(MyEvent.class.getName())) {
+                count++;
+            }
+        }
+        assertEquals(1, count);
+
+    }
+}
+
+class MyEvent extends Event {
+}