diff --git a/src/main/java/org/apache/commons/net/discard/DiscardUDPClient.java b/src/main/java/org/apache/commons/net/discard/DiscardUDPClient.java
index 69f15b8..1830766 100644
--- a/src/main/java/org/apache/commons/net/discard/DiscardUDPClient.java
+++ b/src/main/java/org/apache/commons/net/discard/DiscardUDPClient.java
@@ -41,7 +41,7 @@
     /*** The default discard port.  It is set to 9 according to RFC 863. ***/
     public static final int DEFAULT_PORT = 9;
 
-    private DatagramPacket sendPacket;
+    private final DatagramPacket sendPacket;
 
     public DiscardUDPClient()
     {
diff --git a/src/main/java/org/apache/commons/net/examples/nntp/ExtendedNNTPOps.java b/src/main/java/org/apache/commons/net/examples/nntp/ExtendedNNTPOps.java
index c97a4cf..6df2633 100644
--- a/src/main/java/org/apache/commons/net/examples/nntp/ExtendedNNTPOps.java
+++ b/src/main/java/org/apache/commons/net/examples/nntp/ExtendedNNTPOps.java
@@ -32,7 +32,7 @@
 public class ExtendedNNTPOps {
 
 
-    private NNTPClient client;
+    private final NNTPClient client;
 
     public ExtendedNNTPOps() {
         client = new NNTPClient();
diff --git a/src/main/java/org/apache/commons/net/smtp/RelayPath.java b/src/main/java/org/apache/commons/net/smtp/RelayPath.java
index c49c152..59011a2 100644
--- a/src/main/java/org/apache/commons/net/smtp/RelayPath.java
+++ b/src/main/java/org/apache/commons/net/smtp/RelayPath.java
@@ -31,8 +31,8 @@
 
 public final class RelayPath
 {
-    private Vector<String> path;
-    private String emailAddress;
+    private final Vector<String> path;
+    private final String emailAddress;
 
     /***
      * Create a relay path with the specified email address as the ultimate
diff --git a/src/main/java/org/apache/commons/net/telnet/Telnet.java b/src/main/java/org/apache/commons/net/telnet/Telnet.java
index 80ba39d..ec3cd6d 100644
--- a/src/main/java/org/apache/commons/net/telnet/Telnet.java
+++ b/src/main/java/org/apache/commons/net/telnet/Telnet.java
@@ -61,7 +61,7 @@
     /* public */
     static final int DEFAULT_PORT =  23;
 
-    private int[] doResponse, willResponse, options;
+    private final int[] doResponse, willResponse, options;
 
     /* TERMINAL-TYPE option (start)*/
     /***
diff --git a/src/main/java/org/apache/commons/net/tftp/TFTPErrorPacket.java b/src/main/java/org/apache/commons/net/tftp/TFTPErrorPacket.java
index 50b879b..4c93cad 100644
--- a/src/main/java/org/apache/commons/net/tftp/TFTPErrorPacket.java
+++ b/src/main/java/org/apache/commons/net/tftp/TFTPErrorPacket.java
@@ -70,10 +70,10 @@
     public static final int NO_SUCH_USER = 7;
 
     /*** The error code of this packet. ***/
-    private int error;
+    private final int error;
 
     /*** The error message of this packet. ***/
-    private String message;
+    private final String message;
 
     /***
      * Creates an error packet to be sent to a host at a given port