反垃圾邮件

import java.net.InetAddress;
import java.net.UnknownHostException;

public class Main {
    public static final String blackhole = "sbl.spamhaus.org";
    public static void main(String[] args) {
        if(isSpammer(args[0])) {
            System.out.println("suspected spammer");
        } else {
            System.out.println("reliable user");
        }
    }

    private static boolean isSpammer(String s) {
        try {
            InetAddress ip = InetAddress.getByName(s);
            byte[] b = ip.getAddress();
            String addr = blackhole;
            for(byte item : b) {
                int block = item < 0 ? item + 256 : item;
                addr = block + "." + addr;
            }
            InetAddress.getByName(addr);
            return true;
        } catch(UnknownHostException e) {
            return false;
        }
    }
}