My DD is at Uni, same age and stage, she is now living the life she wants too. I suspect this has happened to your son as well. He is rebelling against your life choices which to some degree is a development stage
I totally agree with Hectare and Holymoly however, please use this as an opportunity to talk to him. Don't feel defensive even if it's hard to hear. Let him talk about why he feels like this, listen hard and if you believe he has a point apologise. The hardest thing I found about being aparent was to accept my children weren't going to be like me so at some stage I needed to stop making choices for them.
Sometime as parents we may hurt our children's feelings (even if we are trying to do the best for them) and if that's the case then we should apologise. Your son is now an adult so you have to reframe your relationship with him. You can show him that adults, even parents must take responsibility for their actions and saying sorry isn't a sign of weakness, it's just learning.
I had a less than perfect childhood, not malicious in anyway just circumstances and bad choices that my parents made. I gained the utmost respect for my mum when she, later in my life, spoke to me about her regrets and how she wished she could turn back the clock but of course she can't.
I now have an excellent relationship with her as do my siblings. My DH on the other hand had an awful childhood but his mum refuses to acknowledge any of it. Nothing can be referred too, events in her mind didn't happen and she blames FIL completely. As a result she has hardly any relationship with her children and grandchildren. That makes her even more angry as she feels she has a right to be treated better so the situation will never improve.
She will be a lonely older woman without her family.
The only tools you can use in this situation are: communication, forgiveness and understanding.