Java won't work?!

So when I try to play Supremacy, it redirects me to the Java application. I do what it tells me, then when it gets to install the green bars won't load, and it said Java 7 update 9 has crashed and it won't work.

Then it won't even let me uninstall Java 7 update 7!

Also, I tried 32 bit and 64 bit, none of them worked. I am using Firefox. So please, can I get help? This is very frustrating.