Last two high priority findbugs errors

Change-Id: I180d9156b49c79980f2b2361ec062e5c1cda64a8
diff --git a/utils/misc/src/main/java/org/onlab/packet/IPv4.java b/utils/misc/src/main/java/org/onlab/packet/IPv4.java
index 28f6a48..574fd1a 100644
--- a/utils/misc/src/main/java/org/onlab/packet/IPv4.java
+++ b/utils/misc/src/main/java/org/onlab/packet/IPv4.java
@@ -32,13 +32,13 @@
     public static final byte PROTOCOL_ICMP = 0x1;
     public static final byte PROTOCOL_TCP = 0x6;
     public static final byte PROTOCOL_UDP = 0x11;
-    public static Map<Byte, Class<? extends IPacket>> protocolClassMap =
+    public static final Map<Byte, Class<? extends IPacket>> PROTOCOL_CLASS_MAP =
             new HashMap<>();
 
     static {
-        IPv4.protocolClassMap.put(IPv4.PROTOCOL_ICMP, ICMP.class);
-        IPv4.protocolClassMap.put(IPv4.PROTOCOL_TCP, TCP.class);
-        IPv4.protocolClassMap.put(IPv4.PROTOCOL_UDP, UDP.class);
+        IPv4.PROTOCOL_CLASS_MAP.put(IPv4.PROTOCOL_ICMP, ICMP.class);
+        IPv4.PROTOCOL_CLASS_MAP.put(IPv4.PROTOCOL_TCP, TCP.class);
+        IPv4.PROTOCOL_CLASS_MAP.put(IPv4.PROTOCOL_UDP, UDP.class);
     }
 
     protected byte version;
@@ -390,8 +390,8 @@
         }
 
         IPacket payload;
-        if (IPv4.protocolClassMap.containsKey(this.protocol)) {
-            final Class<? extends IPacket> clazz = IPv4.protocolClassMap
+        if (IPv4.PROTOCOL_CLASS_MAP.containsKey(this.protocol)) {
+            final Class<? extends IPacket> clazz = IPv4.PROTOCOL_CLASS_MAP
                     .get(this.protocol);
             try {
                 payload = clazz.newInstance();