I apologize in advance if this is a duplicate question, but honestly I don't know how the feature is called. When I search in Eclipse Java auto-complete related questions I can't find it.
When I write Java code and use auto-complete and decide to accept with Enter one of given auto-complete options it will write the method for me, it will populate argument names and a small window will open where I will see in bold on which argument I'm currently on with cursor and what type it is. This bold argument updates in the popup and always puts emphasis on the current argument as I'm writing the arguments.
I hope that is what you are looking for:
In your Eclipse menu, go to Window->Preferences->Java->Editor
There you will find things like:
Hopefully, one of those is what you are looking for.