How to Direct Message a specific person with a Discord Bot

Question

I have tried to DM myself using the code:

User me = new UserById(myId);
me.openPrivateChannel().flatMap(channel -> channel.sendMessage("hello")).queue();

This results in an error message:

[JDA MainWS-ReadThread] ERROR JDA - One of the EventListeners had an uncaught exception
java.lang.UnsupportedOperationException: This User instance only wraps an ID. Other operations are unsupported
    at net.dv8tion.jda.internal.entities.UserById.unsupported(UserById.java:78)
    at net.dv8tion.jda.internal.entities.UserById.openPrivateChannel(UserById.java:132)
    at Commands.onGuildMessageReceived(Commands.java:23)
    at net.dv8tion.jda.api.hooks.ListenerAdapter.onEvent(ListenerAdapter.java:466)
    at net.dv8tion.jda.api.hooks.InterfacedEventManager.handle(InterfacedEventManager.java:96)
    at net.dv8tion.jda.internal.hooks.EventManagerProxy.handleInternally(EventManagerProxy.java:88)
    at net.dv8tion.jda.internal.hooks.EventManagerProxy.handle(EventManagerProxy.java:70)
    at net.dv8tion.jda.internal.JDAImpl.handleEvent(JDAImpl.java:160)
    at net.dv8tion.jda.internal.handle.MessageCreateHandler.handleInternally(MessageCreateHandler.java:97)
    at net.dv8tion.jda.internal.handle.SocketHandler.handle(SocketHandler.java:36)
    at net.dv8tion.jda.internal.requests.WebSocketClient.onDispatch(WebSocketClient.java:952)
    at net.dv8tion.jda.internal.requests.WebSocketClient.onEvent(WebSocketClient.java:839)
    at net.dv8tion.jda.internal.requests.WebSocketClient.handleEvent(WebSocketClient.java:817)
    at net.dv8tion.jda.internal.requests.WebSocketClient.onBinaryMessage(WebSocketClient.java:990)
    at com.neovisionaries.ws.client.ListenerManager.callOnBinaryMessage(ListenerManager.java:385)
    at com.neovisionaries.ws.client.ReadingThread.callOnBinaryMessage(ReadingThread.java:276)
    at com.neovisionaries.ws.client.ReadingThread.handleBinaryFrame(ReadingThread.java:996)
    at com.neovisionaries.ws.client.ReadingThread.handleFrame(ReadingThread.java:755)
    at com.neovisionaries.ws.client.ReadingThread.main(ReadingThread.java:108)
    at com.neovisionaries.ws.client.ReadingThread.runMain(ReadingThread.java:64)
    at com.neovisionaries.ws.client.WebSocketThread.run(WebSocketThread.java:45)

I have looked everywhere, but can't find an answer.

Answer 1

You can use event.getJDA().getUserById() like

User user = event.getJDA().getUserById(id);
user.openPrivateChannel().flatMap(channel -> channel.sendMessage("hlo")).queue();

Also, keep in mind that this would not work if you and your bot do not have a common server or if you have DMs by server members disabled.