android：保存联系人号码并在应用程序中访问它

i am making an app that will allow specific number to ring while phone is silent and i successfully able to change phone state when a specific number cal. Now i need to access contact details, save them and let app access that when that number is calling so that i app can change its sound state. Please help me about resources ideas what things to do etc. I am also giving code of my app.......i am making an app that will allow specific num