Is masturbation a sin when we do it to avoid intercourse with other people?

I masturbate to avoid having sex with other people. I've masturbated quite a lot. I don't want to have sexual intercourse with anyone else though I love sex. I've been keeping my body away from sexual desire with other men and found masturbation as a good feeling. I've never had any imagination of anyone else or rarely (if it does, it should be a person that I really like or dating with but I just keep desire away from him, again rarely). I also have known that masturbation could prevent sexual assaults. Is this a sin or not?