Findbugs all over:

- Serializable
 - hashCode()
 - Make DataStructureImpl Serializable (removed from DataStructure in 2005)

apps/routerconsole/java/src/net/i2p/router/update/ConsoleUpdateManager.java

@@ -1584,6 +1584,12 @@ public class ConsoleUpdateManager implements UpdateManager, RouterApp {
             return super.equals(o) && (o instanceof VersionAvailable);
         }
 
+        @Override
+        public int hashCode() {
+            // findbugs
+            return super.hashCode();
+        }
+
         @Override
         public String toString() {
             return "VersionAvailable \"" + version + "\" " + sourceMap +