The type of Java you specialize in will make a difference as will the size of the company and sector (fintech will pay more, for example).

With six years experience, anything between 100k and 120k. If it is a team lead roll, you should add at least 10k to that.
Of the last few jobs I've had here over the years, the best paid in almost all cases was a female employee, compared to people doing similar jobs, one of whom would often complain about the gender pay gap, despite this. In all cases, they were Swiss, while the lesser paid employees were foreigners.

So while I have no doubt employers will use any excuse to pay someone less, you're far more likely to be paid less for being a foreigner than a woman.

You can check https://swissdevjobs.ch/ for up to date salaries in different places (the site does not have UBS/CS/Google and other Big Co where you might get a better package, especially Google)

I think you could have negotiated a bit more.
You should have replied 120K for the 115K offer.
Then they would have replied with an offer containing 117 or 118, which you could have accepted.