1.use putIfAbsent instead of put method of ConcurrentHashMap 2.add test code

broker/src/test/java/org/apache/rocketmq/broker/BrokerStatsManagerTest.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.broker;
+
+import static org.apache.rocketmq.store.stats.BrokerStatsManager.TOPIC_PUT_NUMS;
+
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+import org.apache.rocketmq.common.ThreadFactoryImpl;
+import org.apache.rocketmq.store.stats.BrokerStatsManager;
+import org.junit.Before;
+import org.junit.Test;
+
+public class BrokerStatsManagerTest {
+
+    private BrokerStatsManager brokerStatsManager;
+    private ThreadPoolExecutor executor;
+    @Before
+    public void init() {
+        brokerStatsManager = new BrokerStatsManager("DefaultCluster");
+        executor = new ThreadPoolExecutor(100, 200, 10, TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(1000), new ThreadFactoryImpl("testMultiThread"));
+    }
+
+    @Test
+    public void test_getAndCreateStatsItem_multiThread() throws InterruptedException {
+
+        for(int i =0; i < 10000; i++) {
+            executor.submit(new Runnable() {
+                @Override
+                public void run() {
+                    brokerStatsManager.incTopicPutNums("topicTest", 2, 1);
+                }
+            });
+        }
+        Thread.sleep(5000);
+        System.out.println(brokerStatsManager.getStatsItem(TOPIC_PUT_NUMS,"topicTest").getValue());
+    }
+}
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