public static Name
fromAddress(String addr) throws UnknownHostException {
	byte [] array = Address.toByteArray(addr, Address.IPv4);
	if (array == null)
		array = Address.toByteArray(addr, Address.IPv6);
	if (array == null)
		throw new UnknownHostException("Invalid IP address");
	return fromAddress(array);
}
Creates a reverse map name corresponding to an address contained in
a String.
@param addr The address from which to build a name.
@return The name corresponding to the address in the reverse map.
@throws UnknownHostException The string does not contain a valid address.
src/main/java/core/org/xbill/DNS/ReverseMap.java