inviting friends to your server minecraft java
First, use whitelist on to enable the whitelist, which will only allow specified players to join.
You can add players to the whitelist using whitelist add <targets>
<targets> is defined as:
Must be a collection of game profiles (player profiles), which can be a player name (must be a real one if the server is in online mode), or a player-type target selector. Specifies the player profile(s) to be added to or removed from the whitelist.
From the wiki