Can't find user by id

[RTX4O9O]

So i tried to code a bot that dms people
But idk why I wasnt able to find user

Here is my code

package me.rtx4090;
import net.dv8tion.jda.api.JDA;
import net.dv8tion.jda.api.JDABuilder;
import net.dv8tion.jda.api.events.guild.GuildReadyEvent;
import net.dv8tion.jda.api.hooks.ListenerAdapter;
import net.dv8tion.jda.api.entities.User;

public class Main extends ListenerAdapter {
    private JDA jda;

    public Main() {
        String botToken = "(censored)";
        jda = JDABuilder.createDefault(botToken).addEventListeners(this).build();
    }

    public static void main(String[] args) {
        new Main();
    }

    @Override
    public void onGuildReady(GuildReadyEvent event) {
        System.out.println("All members in the guild " + event.getGuild().getName() + " have been downloaded.");

        // Now you can be sure that all server members are loaded
        sendPrivateMessage();
    }

    private void sendPrivateMessage() {
        String recipientUserId = "(censored)"; 
        String messageContent = "L";

        User recipient = jda.getUserById(recipientUserId);
        System.out.println(recipient);

        if (recipient != null) {
            recipient.openPrivateChannel().queue(privateChannel -> {
                privateChannel.sendMessage(messageContent).queue();
                System.out.println("Message has been sent to " + recipient.getAsTag() + " successfully");
            });
        } else {
            System.out.println("Can't find the user. Please make sure you've used the correct ID");
        }
    }
}

And here is the console

12:28:54 AM: Executing ':Main.main()'...

> Task :compileJava UP-TO-DATE
> Task :processResources NO-SOURCE
> Task :classes UP-TO-DATE

> Task :Main.main()
All members in the guild Private have been downloaded.
null
Can't find the user. Please make sure you've used the correct ID
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
SLF4J: Failed to load class "org.slf4j.impl.StaticMDCBinder".
SLF4J: Defaulting to no-operation MDCAdapter implementation.
SLF4J: See http://www.slf4j.org/codes.html#no_static_mdc_binder for further details.
[main] INFO JDA - Login Successful!
[JDA MainWS-ReadThread] INFO WebSocketClient - Connected to WebSocket
[JDA MainWS-ReadThread] INFO JDA - Finished Loading!

Please help me to solve this 🙏🙏

[jasonjente]

The method you are invoking uses the JDA cache for the id which probably has not have been invalidated yet.

What I have been using on my project to send private message to a user looks like this

//get the user from the event and filter based on your preferences. I used the member.getRoles() to keep only the objects that belong to a role I have defined.
List<Member> members = event.getGuild().loadMembers()
                    .get()
                    .stream()
                    .filter(member -> member.getRoles().contains(ROLE))
                    .collect(Collectors.toList());
                    
for (Member member : members)
     PrivateChannel channel = member.getUser().openPrivateChannel().complete();
     channel.sendMessage(message).queue();

Also if you have the guild Id and the user ID you can do something like the following:

Member caller = jda.getGuildById(guildId).loadMembers()
                    .get()
                    .stream()
                    .filter(m -> m.getUser().getId().equals(userId))
                    .collect(Collectors.toList()).get(0);

I would recommend to read the Guild.java (findMembers method), Member.java and JDA.java (retrieveUserById method) as they might provide some more insight on how to proceed.

Hope this helps :)

[MinnDevelopment]

This has already been answered on stackoverflow. The right approach is to use openPrivateChannelById instead.