Fix issues found by FindBugs: MS_SHOULD_BE_FINAL

http://findbugs.sourceforge.net/bugDescriptions.html#MS_SHOULD_BE_FINAL

Change-Id: I9c08c8002722eb93b4f7bab8f47737a6a6aea38d
diff --git a/src/main/java/net/onrc/onos/core/packet/BSN.java b/src/main/java/net/onrc/onos/core/packet/BSN.java
index dedabd5..0de2bca 100644
--- a/src/main/java/net/onrc/onos/core/packet/BSN.java
+++ b/src/main/java/net/onrc/onos/core/packet/BSN.java
@@ -31,12 +31,12 @@
     public static final short BSN_VERSION_CURRENT = 0x0;
     public static final short BSN_TYPE_PROBE = 0x1;
     public static final short BSN_TYPE_BDDP = 0x2;
-    public static Map<Short, Class<? extends IPacket>> typeClassMap;
+    public static final Map<Short, Class<? extends IPacket>> TYPE_CLASS_MAP;
 
     static {
-        typeClassMap = new HashMap<Short, Class<? extends IPacket>>();
-        typeClassMap.put(BSN_TYPE_PROBE, BSNPROBE.class);
-        typeClassMap.put(BSN_TYPE_BDDP, LLDP.class);
+        TYPE_CLASS_MAP = new HashMap<Short, Class<? extends IPacket>>();
+        TYPE_CLASS_MAP.put(BSN_TYPE_PROBE, BSNPROBE.class);
+        TYPE_CLASS_MAP.put(BSN_TYPE_BDDP, LLDP.class);
     }
 
     protected short type;
@@ -112,8 +112,8 @@
         }
 
         IPacket payload;
-        if (typeClassMap.containsKey(this.type)) {
-            Class<? extends IPacket> clazz = typeClassMap.get(this.type);
+        if (TYPE_CLASS_MAP.containsKey(this.type)) {
+            Class<? extends IPacket> clazz = TYPE_CLASS_MAP.get(this.type);
             try {
                 payload = clazz.newInstance();
             } catch (Exception e) {
@@ -161,8 +161,8 @@
     public String toString() {
         StringBuffer sb = new StringBuffer("\n");
         sb.append("BSN packet");
-        if (typeClassMap.containsKey(this.type))
-            sb.append(" type: " + typeClassMap.get(this.type).getCanonicalName());
+        if (TYPE_CLASS_MAP.containsKey(this.type))
+            sb.append(" type: " + TYPE_CLASS_MAP.get(this.type).getCanonicalName());
         else
             sb.append(" type: " + this.type);