Getting Unique Device Id in android

We can get unique id by using telephony manager and android id.
But better to generate unique id by using both

 TelephonyManager manager = (TelephonyManager)this.getSystemService(Context.TELEPHONY_SERVICE);
                       String imei = manager.getDeviceId();
                     String androidId =android.provider.Settings.Secure.getString(getContentResolver(), android.provider.Settings.Secure.ANDROID_ID);
                      UUID deviceUuid = new UUID(androidId.hashCode(), (imei.hashCode()<<32));
                      System.out.println("deviceUuid1   "+deviceUuid.toString());