InetAddress.getByName gives strage results.

Question

hello.
I'm interested in integer representation of IP address.
However the inetAddress.getByName gives me strange results.
public static void main(String[] args) throws UnknownHostException {
            InetAddress test1 = InetAddress.getByName("127.0.0.1"); 
            System.out.println(String.valueOf(test1.hashCode()));  //prints 2130706433, that's great.
            InetAddress test2 = InetAddress.getByName("192.168.5.18");
            System.out.println(String.valueOf(test2.hashCode()));  *//prints -1062730478, that's wrong!! should be 3232236818 why negative ?*
            InetAddress test3 = InetAddress.getByName("79.182.113.50");
            System.out.println(String.valueOf(test3.hashCode())); // prints 1337356594, that's ok.
    }I'd like to know what I'm missing here , this seems to be a glitch.

Answer 1

uprooter wrote:
http://www.aboutmyip.com/AboutMyXApp/IP2Integer.jsp
That's even a JSP page :)
As the results showed, it's not a dumb hash code. it's the real int representation of the IP address.
Edited by: uprooter on Dec 8, 2008 9:41 AMI haven't clicked that, but if by "real int representation", you mean that it's just taking the 4 octets of the IP adress and mashing them together into an int, with the first octet as the high-order byte, then simple logic (the pigeonhole principle) will tell you that half of the possible IP addresses MUST have negative hashCodes, and an understanding of [twos complement|http://en.wikipedia.org/wiki/Twos_complement] will tell you that 192.168.5.18 in particular will definitely be negative.