docs: public static boolean isIpv4(String hostName) {
  		int periodCount = 0;
  		int numberCount = 0;
  		int lowerCount = 0;
  		int upperCount = 0;
  		int otherCount = 0;
  		
  		for(int i = 0; i < hostName.length(); i++ ) {
  			char myChar = hostName.charAt(i);
  			if (myChar=='.') {
  				periodCount++;
  			} else if (myChar >= '0' && myChar <= '9') {
  				numberCount++;
  			} else if (myChar >= 'a' & myChar <= 'z') {
  				lowerCount++;
  			} else if (myChar >= 'A' & myChar <= 'Z') {
  				upperCount++;
  			} else {
  				otherCount++;
  			}
  		}
  		
  		if (periodCount==3 && numberCount >= 4 && lowerCount==0 && upperCount==0 && otherCount==0) {
  			return true;
  		} else {
  			return false;
  		}
  	}