To the point:
I generally prefer email, but Twitter DMs are also a good way to get in touch, particularly if it's urgent. If you just want to chat with me or a few other Java geeks, give the Discord a go.
If your request is a technical Java question, I encourage you to ask it in a public forum, preferably on StackOverflow, so everybody can benefit from the answer. Feel free to send me a link to your question if you think I can help.