How to tell if a scanned FM radio channel is a valid channel or invalid using Android programming?

I need to find out the correct and invalid channels among the scanned channels. for example, if 10 channels are scanned, of which 8 are playing properly and 2 are not valid channels, only noise is heard, then how can I solve this using android program. I am aware if you would like more information. I am viewing it on an Android phone. If there is any other solution, such as using digital signal processing, FFT, etc., please suggest the correct links.