TestDns.java

import java.net.InetSocketAddress;

public class TestDns {
    public static void main(String[] args) {
        
        System.out.println(sun.net.InetAddressCachePolicy.get());
        
        InetSocketAddress unresolved = InetSocketAddress.createUnresolved("10.228.174.223", 8020);
        System.out.println(unresolved.toString());  // prints 10.228.174.223:8020
        System.out.println(unresolved.getHostName());  // prints 10.228.174.223:8020
        System.out.println(unresolved.toString());  // prints 10.228.174.223:8020
        
        InetSocketAddress resolved = new InetSocketAddress("10.228.174.223", 8020);
        System.out.println(resolved.toString());  // prints /10.228.174.223:8020
        System.out.println(resolved.getHostName());  // prints ip-10-228-174-223.eu-west-1.compute.interna
        System.out.println(resolved.toString());  // prints ip-10-228-174-223.eu-west-1.compute.interna/10.228.174.223:8020
    }
}