public FeedKey intern(final FeedKey feedKey) {
            if (feedKey != null) {
                final FeedKey prevVal = map.putIfAbsent(feedKey, feedKey);
                return prevVal != null
                        ? prevVal
                        : feedKey;
            } else {
                return null;
            }
        }
Allows re-use of {@link FeedKey} instances by a thread.
Not thread safe.
stroom-proxy/stroom-proxy-repo/src/main/java/stroom/proxy/repo/FeedKey.java