I honestly just don't care about my friend who is an addict anymore.
I'm sorry to hear that. What type of addiction is he going thruough?
He's an alcoholic, but he doesn't let anyone know it.
I know it can be tough to deal with friends who are suffering with addiction, but you should be there to support him. Tell your friend that you're worried they're drinking too much, and let them know you want to be supportive.
I've tried to talk to him before, but he doesn't listen.
If you have told him how you feel, but he still won't do anything to make changes, then an intervention might help. There are services out there to help plan them, and it might help save his life. Having his friends and family there to tell him they love him and are worried might help him get sober.