code: @Override
      public void invalidate() {
          // thread-safety on cache operations
          synchronized (requestCache) {
              requestCache = new HashMap<String, ResponseCtx>(CACHE_SIZE);
              requestCacheTimeTracker = new HashMap<String, Long>(CACHE_SIZE);
              requestCacheUsageTracker = new ArrayList<String>(CACHE_SIZE);
          }
      }
docs: /*
  (non-Javadoc)
  @see org.fcrepo.server.security.xacml.pep.ResponseCache#invalidate()