Fix integer overflow.

common/src/main/java/org/apache/rocketmq/common/BrokerConfig.java

@@ -91,7 +91,7 @@ public class BrokerConfig {
     private boolean slaveReadEnable = false;
 
     private boolean disableConsumeIfConsumerReadSlowly = false;
-    private long consumerFallbehindThreshold = 1024 * 1024 * 1024 * 16;
+    private long consumerFallbehindThreshold = 1024L * 1024 * 1024 * 16;
 
     private long waitTimeMillsInSendQueue = 200;
 

common/src/test/java/org/apache/rocketmq/common/BrokerConfigTest.java

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.rocketmq.common;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class BrokerConfigTest {
+
+    @Test
+    public void testConsumerFallBehindThresholdOverflow() {
+        long expect = 1024L * 1024 * 1024 * 16;
+        Assert.assertEquals(expect, new BrokerConfig().getConsumerFallbehindThreshold());
+    }
+
+}
\ No newline at end of file