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]);
    }
}

And I got:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at demo.Lookup.main(Lookup.java:19)

Thanks

CodePudding user response：

the "args" from the main method is passing in by parameter

public static void main(String[] args)

Assuming that you are compiling the codes using command line:

javac demo\Lookup.java (I am using windows here) 

you can pass in the parameter when you execute the codes using command line

java demo.Lookup <lookup ip address here>

if you are using IDE such as Eclipse, you can configure your "Run Configuration" to pass in IP address in the "Program Arguments"

CodePudding user response：

No args are passed into your args parameter wherever you are calling this function. So when you try to get the first value, there is nothing there.