update

@@ -15,7 +15,9 @@ import org.springframework.stereotype.Service;
 
 import java.io.UnsupportedEncodingException;
 import java.net.URLEncoder;
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -43,7 +45,7 @@ public class AlarmMsgServiceImpl implements AlarmMsgService {
     private static final int CONTENT_SUB_LENGTH = 250;
 
 
-    public static final String DEFAULT_SENT_LOCK="sent_lock";
+    public static final String DEFAULT_SENT_LOCK = "sent_lock";
 
     private Map<String, Long> msgSentLogMap = new HashMap<>();
 
@@ -179,8 +181,9 @@ public class AlarmMsgServiceImpl implements AlarmMsgService {
     @Scheduled(fixedRate = 5 * 60 * 1000)
     public void clearMsgSentLog() {
 
-        synchronized (DEFAULT_SENT_LOCK)
-        {
+        synchronized (DEFAULT_SENT_LOCK) {
+            List<String> clearKeyList = new ArrayList<>();
+
             for (Map.Entry<String, Long> entry : msgSentLogMap.entrySet()) {
 
                 String sentKey = entry.getKey();
@@ -191,9 +194,14 @@ public class AlarmMsgServiceImpl implements AlarmMsgService {
 
                 if (5 * 60 * 1000 <= (sentAgainTime - sentTime)) {
 
-                    msgSentLogMap.remove(sentKey);
+                    clearKeyList.add(sentKey);
                 }
             }
+
+            for (String clearKey : clearKeyList) {
+
+                msgSentLogMap.remove(clearKey);
+            }
         }
     }
 }