try {
    // Get hostname by textual representation of IP address
    InetAddress addr = InetAddress.getByName("127.0.0.1");

    // Get hostname by a byte array containing the IP address
    byte[] ipAddr = new byte[]{127, 0, 0, 1};
    addr = InetAddress.getByAddress(ipAddr);

    // Get the host name
    String hostname = addr.getHostName();

    // Get canonical host name
    String hostnameCanonical = addr.getCanonicalHostName();
} catch (UnknownHostException e) {
}