1. Getting the IP Address of a Hostname

    try 
    {
        InetAddress addr = InetAddress.getByName("yahoo.com");
        byte[] ipAddr = addr.getAddress();

        // Convert to dot representation
        String ipAddrStr = "";
        for (int i=0; i<ipAddr.length; i++) {
            if (i > 0) {
                ipAddrStr += ".";
            }
            ipAddrStr += ipAddr[i]&0xFF;
        }
    } 
    catch (UnknownHostException e) {
    }

2. Getting the Hostname of an IP Address

This example attempts to retrieve the hostname for an IP address. Note that getHostName() may not succeed, in which case it simply returns the IP address.

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) {
    }

3. Getting the IP Address and Hostname of the Local Machine

    try {
        InetAddress addr = InetAddress.getLocalHost();

        // Get IP Address
        byte[] ipAddr = addr.getAddress();

        // Get hostname
        String hostname = addr.getHostName();
    } catch (UnknownHostException e) {
    }