code: public byte[] get(String cfName, ReadOptions readOptions, String key) throws RocksDbException {
          if (cfName == null) {
              cfName = DEFAULT_COLUMN_FAMILY;
          }
          ColumnFamilyHandle cfh = columnFamilyHandles.get(cfName);
          if (cfh == null) {
              throw new RocksDbException.ColumnFamilyNotExists(cfName);
          }
          return get(cfh, readOptions, key.getBytes(StandardCharsets.UTF_8));
      }
docs: Gets a value from a column family, specifying read options.
  
  @param cfName
  @param readOptions
  @param key
  @return
  @throws RocksDbException