Polish async send message sample

example/src/main/java/org/apache/rocketmq/example/simple/AsyncProducer.java

@@ -17,6 +17,8 @@
 package org.apache.rocketmq.example.simple;
 
 import java.io.UnsupportedEncodingException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
 import org.apache.rocketmq.client.exception.MQClientException;
 import org.apache.rocketmq.client.producer.DefaultMQProducer;
 import org.apache.rocketmq.client.producer.SendCallback;
@@ -32,7 +34,9 @@ public class AsyncProducer {
         producer.start();
         producer.setRetryTimesWhenSendAsyncFailed(0);
 
-        for (int i = 0; i < 10000000; i++) {
+        int messageCount = 100;
+        final CountDownLatch countDownLatch = new CountDownLatch(messageCount);
+        for (int i = 0; i < messageCount; i++) {
             try {
                 final int index = i;
                 Message msg = new Message("Jodie_topic_1023",
@@ -42,11 +46,13 @@ public class AsyncProducer {
                 producer.send(msg, new SendCallback() {
                     @Override
                     public void onSuccess(SendResult sendResult) {
+                        countDownLatch.countDown();
                         System.out.printf("%-10d OK %s %n", index, sendResult.getMsgId());
                     }
 
                     @Override
                     public void onException(Throwable e) {
+                        countDownLatch.countDown();
                         System.out.printf("%-10d Exception %s %n", index, e);
                         e.printStackTrace();
                     }
@@ -55,6 +61,7 @@ public class AsyncProducer {
                 e.printStackTrace();
             }
         }
+        countDownLatch.await(5, TimeUnit.SECONDS);
         producer.shutdown();
     }
 }