Java reverse DNS name resolution

ResolverHelper.java

import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
public class ResolverHelper {
  public static void main(String[] args) throws UnknownHostException {
    InetAddress ia = InetAddress.getByName(args[0]);
    InetSocketAddress isa = new InetSocketAddress(args[0], 12345);
    System.out.println(ia.getCanonicalHostName());
    System.out.println(isa.getAddress().getCanonicalHostName());
  }
}