[ISSUE# 2325] Use CopyOnWriteArrayList to avoid possible thread safety issues

broker/src/main/java/org/apache/rocketmq/broker/out/BrokerOuterAPI.java

@@ -19,7 +19,6 @@ package org.apache.rocketmq.broker.out;
 import java.io.UnsupportedEncodingException;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Vector;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
@@ -123,7 +122,7 @@ public class BrokerOuterAPI {
         final int timeoutMills,
         final boolean compressed) {
 
-        final List<RegisterBrokerResult> registerBrokerResultList = new Vector<>();
+        final List<RegisterBrokerResult> registerBrokerResultList = new CopyOnWriteArrayList<>();
         List<String> nameServerAddressList = this.remotingClient.getNameServerAddressList();
         if (nameServerAddressList != null && nameServerAddressList.size() > 0) {