Sockets for Clients - Java Network Programming - page 273

The main functionality of the class is in one method, lookUpNames() . The lookUp
Names() method returns a String containing the whois response to a given query. The
arguments specify the string to search for, what kind of record to search for, which
database to search in, and whether an exact match is required. I could have used strings
or int constants to specify the kind of record to search for and the database to search
in, but because there are only a small number of valid values, lookUpNames() defines
enums with a fixed number of members instead. This solution provides much stricter
compile-time type-checking and guarantees the Whois class won't have to handle an
unexpected value.
Example 8-7. The Whois class
import java.net.* ;
import java.io.* ;
public class Whois {
public final static int DEFAULT_PORT = 43 ;
public final static String DEFAULT_HOST = "whois.internic.net" ;
private int port = DEFAULT_PORT ;
private InetAddress host ;
public Whois ( InetAddress host , int port ) {
this . host = host ;
this . port = port ;
}
public Whois ( InetAddress host ) {
this ( host , DEFAULT_PORT );
}
public Whois ( String hostname , int port )
throws UnknownHostException {
this ( InetAddress . getByName ( hostname ), port );
}
public Whois ( String hostname ) throws UnknownHostException {
this ( InetAddress . getByName ( hostname ), DEFAULT_PORT );
}
public Whois () throws UnknownHostException {
this ( DEFAULT_HOST , DEFAULT_PORT );
}
// Items to search for
public enum SearchFor {
ANY ( "Any" ), NETWORK ( "Network" ), PERSON ( "Person" ), HOST ( "Host" ),
DOMAIN ( "Domain" ), ORGANIZATION ( "Organization" ), GROUP ( "Group" ),
GATEWAY ( "Gateway" ), ASN ( "ASN" );