java file

public class DetectNumberActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

    }
        public String returnNumber() {
            String number = null;
            String service = Context.TELEPHONY_SERVICE;
            TelephonyManager tel_manager = (TelephonyManager) getSystemService(service);
            int device_type = tel_manager.getPhoneType();

            switch (device_type) {
                  case (TelephonyManager.PHONE_TYPE_CDMA):
                     number = tel_manager.getLine1Number();
                  Log.e("", "");
                  break;
                  default:
                    //return something else
                    number = "no number";
                   break;
            }
            return number;
       }

    }