docs: public void removeAndAdd(final String toRemove, final String toAdd) {
        writeLock.lock();
        try {
           FileListCacheValue fileList = getFileList();
           boolean done = fileList.addAndRemove(toAdd, toRemove);
           if (done) {
              updateFileList(fileList);
              if (trace) {
                 log.trace("Updated file listing: added " + toAdd + " and removed " + toRemove);
              }
           }
        } finally {
           writeLock.unlock();
        }
     }