It won't let me use servers. It keeps crashing.

Put the summary of the bug you're having here

What I expected to happen was...:
To get online to my favorite server. I had to reinstall Minecraft, because I had some PC problems so I had to wipe my whole PC. Then it asked me something about Java and I accidently clicked no... I think that's the problem

What actually happened was...:
Every time I tried to get onto the server it would do a crash report

Steps to Reproduce:
1. go to servers
2. pick a server
3. Then it crashes