FTPSERVER-405 Make Map field final (improve thread-safety)

git-svn-id: https://svn.apache.org/repos/asf/mina/ftpserver/trunk@1094576 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/core/src/main/java/org/apache/ftpserver/ftpletcontainer/impl/DefaultFtpletContainer.java b/core/src/main/java/org/apache/ftpserver/ftpletcontainer/impl/DefaultFtpletContainer.java
index 7d85fa3..a1051c2 100644
--- a/core/src/main/java/org/apache/ftpserver/ftpletcontainer/impl/DefaultFtpletContainer.java
+++ b/core/src/main/java/org/apache/ftpserver/ftpletcontainer/impl/DefaultFtpletContainer.java
@@ -49,9 +49,10 @@
     private final Logger LOG = LoggerFactory
             .getLogger(DefaultFtpletContainer.class);
 
-    private Map<String, Ftplet> ftplets = new ConcurrentHashMap<String, Ftplet>();
+    private final Map<String, Ftplet> ftplets ;
 
     public DefaultFtpletContainer() {
+        this(new ConcurrentHashMap<String, Ftplet>());
     }
     
     public DefaultFtpletContainer(Map<String, Ftplet> ftplets) {