Make public fields final where possible

Class fields initialized via the constructor should be final.

Also mark leaking byte[] instances with a FIXME. API users consider them
immutable, but they are vulnerable to System.arrayCopy().

Also fixes constructor arguments so they do not use underscores, which
is prohibited by Java 9.

Change-Id: I393d55ed7234149cb3604bc92b2cb1d1207c55dc
Signed-off-by: Robert Varga <nite@hq.sk>
diff --git a/vpp-japi/japi/org/openvpp/vppjapi/vppIPv6Address.java b/vpp-japi/japi/org/openvpp/vppjapi/vppIPv6Address.java
index efaa89c..7bf10f2 100644
--- a/vpp-japi/japi/org/openvpp/vppjapi/vppIPv6Address.java
+++ b/vpp-japi/japi/org/openvpp/vppjapi/vppIPv6Address.java
@@ -16,8 +16,9 @@
 package org.openvpp.vppjapi;
 
 public class vppIPv6Address {
-    public byte[] ip;
-    public byte prefixLength;
+    // FIXME: this is dangerous
+    public final byte[] ip;
+    public final byte prefixLength;
 
     public vppIPv6Address(byte[] _ip, byte _prefixLength) {
         ip = _ip;