BuildBedrockwithPowerNukkitX.

public final class WelcomePlugin extends PluginBase {

    @Override
    public void onEnable() {
        getLogger().info("WelcomePlugin ready.");
    }

    @EventListener
    public static final class PlayerListener implements Listener {

        @EventHandler
        public void onJoin(PlayerJoinEvent event) {
            event.getPlayer().sendMessage("Welcome to the server!");
        }
    }
}