code: @Override
    public boolean collectionExists(String collectionName) {
      CollectionMetaData collectionMeta = cmdMap.get(collectionName);
      if(null == collectionMeta) {
        return false;
      }
      collectionMeta.getCollectionLock().readLock().lock();
      try {
        return collectionsRef.get().containsKey(collectionName);
      } finally {
        collectionMeta.getCollectionLock().readLock().unlock();
      }
    }
docs: /* (non-Javadoc)
  @see io.jsondb.JsonDBOperations#collectionExists(java.lang.String)