User data scrubbing SFDC

scrub_user_data.cls

public static String generateRandomString(Integer len) {
    final String chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz';
    String randStr = '';
    while (randStr.length() < len) {
       Integer idx = Math.mod(Math.abs(Crypto.getRandomInteger()), chars.length());
       randStr += chars.substring(idx, idx+1);
    }
    return randStr; 
}

List<String> doNotEditIds = new List<String>{ '005U0000003TZ49', '0050B0000080YI2QAM', '0050B000007zsmKQAQ', '0050B000007zsmLQAQ'};
Set<String> unableToDeactivateIds = new Set<String> {'0050B000007C3ZwQAK', '0050B000007zsmKQAQ', '005U0000005sd5PIAQ','0050B000006qMw2QAE','005U0000003FOvxIAG','0050B0000080e7ZQAQ', '005U0000004PBGOIA4', '0050B000006qCyN', '0050B0000080Dpy', '005U0000006FECa'}; 

List<User> allUsers;
allUsers = [SELECT Id, isActive from User where Id NOT IN :doNotEditIds and UserType != 'AutomatedProcess' AND Phone != 'FIXED' limit 148];

System.Debug(allUsers.size());
for(User u: allUsers)
{ 
   String garbageEmail = 'interview=' + generateRandomString(10) + '@interview.com';
   u.FirstName = generateRandomString(5);
   u.LastName = generateRandomString(5);
   u.PostalCode = '';
   u.UserName = garbageEmail;
   u.Email = garbageEmail;
   u.MobilePhone = '';
   u.Phone = 'FIXED';
   if(!unableToDeactivateIds.contains(u.Id)) {
      u.IsActive = false;
   }
   try {
     update u;
   } catch (Exception e) {
     System.Debug(e);
   } 
}