code: public static String firstValidOf(String... strings) {
  		if(strings != null) {
  			for(int i = 0; i < strings.length; ++i) {
  				if(Strings.isValid(strings[i])) {
  					return strings[i];
  				}
  			}
  		}
  		return null;	
  	}
docs: Returns the first valid string in the given set.
  
  @param strings
  a set of strings.
  @return
  the first valid string in the set, or null if none is valid.