| Methods Summary |
|---|
| private static boolean | isHostname(java.lang.String host)
// Is this an IPv6 address?
if (host.indexOf(':") != -1) return false;
char[] ca = host.toCharArray();
// if we see a character that is neither a digit nor a period
// then host is probably a hostname
for (int i = 0; i < ca.length; i++) {
if (!Character.isDigit(ca[i])) {
if (ca[i] != '.") return true;
}
}
// Everything was either a digit or a period
// so host looks like an IPv4 address in dotted quad format
return false;
|
| private static java.lang.String | lookup(java.lang.String host)
InetAddress node;
// get the bytes of the IP address
try {
node = InetAddress.getByName(host);
}
catch (UnknownHostException ex) {
return "Cannot find host " + host;
}
if (isHostname(host)) {
return node.getHostAddress();
}
else { // this is an IP address
return node.getHostName();
}
|
| public static void | main(java.lang.String[] args)
if (args.length > 0) { // use command line
for (int i = 0; i < args.length; i++) {
System.out.println(lookup(args[i]));
}
}
else {
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter names and IP addresses. Enter \"exit\" to quit.");
try {
while (true) {
String host = in.readLine();
if (host.equalsIgnoreCase("exit") || host.equalsIgnoreCase("quit")) {
break;
}
System.out.println(lookup(host));
}
}
catch (IOException ex) {
System.err.println(ex);
}
}
|
