@Override
    public void clear() {
        LOGGER.trace(() -> buildMessage("clear"));

        // Read lock as we are not changing the reference to the cache.
        // The cache has its own concurrency protection at the entry level.
        CacheUtil.clear(getCache());
    }
Subclasses should implement this method to add to the cacheBuilder as required
and return a cache built from cacheBuilder. The builder already has a
removalNotificationConsumer if applicable and recordStats has been set.
stroom-cache/stroom-cache-impl/src/main/java/stroom/cache/impl/AbstractStroomCache.java