Predict/Identify country codes for phone numbers

I have list of mobile phone numbers from different countries from Android contacts. Some of these contacts have country codes while some of them don't.

So, a solution could be:

1. Get all supported country codes of the world
2. Loop a number with all the country codes
3. Check validity of number

This could be one way to predict a number for supported countries. I am wondering if there is a better way to approach this problem?

PhoneNumberUtil phoneUtil = PhoneNumberUtil.getInstance();

String numberStr = "04157012311";
Set<String> allRegions = phoneUtil.getSupportedRegions();
Set<String> validRegions = new LinkedHashSet<String>();

for (String region : allRegions) {
  try {
    if (phoneUtil.isValid(phoneUtil.parse(numberStr, region))) {
      validRegions.add(region);
    }        
  } catch (NumberParseException e) {
    // Handle NumberParseException
  }
}

validRegions will contain ISO codes of regions where your phone number can be located