线程“main”java中出现异常。lang.ArrayIndexOutOfBoundsException:演示时为0。查找。main(Lookup.java:19)

package demo;
import java.net.*;

public class Lookup {
    private InetAddress inet = null;
    public void resolve(String host){
        try{
            inet = InetAddress.getByName(host);
            System.out.println("Host name :" +inet.getHostName());
            System.out.println("IP Address:" +inet.getHostAddress());
        }
        catch(UnknownHostException e){
            e.printStackTrace();
        }
    }

    public static void main(String[] args){
        Lookup lookup = new Lookup();
        lookup.resolve(args[0]);
    }
}

我得到了:
线程“main”java中出现异常。lang.ArrayIndexOutOfBoundsException:0 在演示中。查找。main(Lookup.java:19)

谢谢