Why is Member null when using Guild.getMemberById(...)?

[DomiWe]

jda.getGuildById(...).getMemberById(...)

I get null, but on the Server in my Guild the Member exists.

[RedDaedalus]

When using methods such as getMember() or getMemberById(String) there's a possibility that the returned Member is null.
There can be many reasons, but most of the time the cause is that a Member isn't cached (yet).

When using createLight(String) or createDefault(String) for building a JDA/ShardManager instance JDA will disable Member Caching and Member Chunking.
This has the side-effect that JDA doesn't "know" a member yet and therefore returns null since a Member is nullable.

There are several options that you can do instead:

• If you get the member of a Message-based event such as GuildMessageReceivedEvent, use getAuthor() instead as this returns a User object which won't be null.
• Use retrieveMember(). This is a RestAction, so don't forget to queue() it!
• Have Member Caching and Member Chunking active. This requires the priviledged GUILD_MEMBER intend to be enabled.

Please read this page for more info:
https://github.com/DV8FromTheWorld/JDA/wiki/Gateway-Intents-and-Member-Cache-Policy