userId property
Identifier of the shared user. This number may have more than 32 significant bits and some programming languages may have difficulty/silent defects in interpreting it. But it has at most 52 significant bits, so 64-bit integers or double-precision float types are safe for storing these identifiers. The bot may not have access to the user and could be unable to use this identifier unless the user is already known to the bot by some other means.
Implementation
final int userId;