CustomDNS.java

package com.yourapp;

import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;

import okhttp3.Dns;

public class CustomDNS implements Dns {
    @Override
    public List<InetAddress> lookup(String hostname) throws UnknownHostException {
        InetAddress[] addresses = InetAddress.getAllByName(hostname);
        if (addresses == null || addresses.length == 0) {
            Dns.SYSTEM.lookup(hostname);
        }

        // Get IPv4 first.
        ArrayList<InetAddress> result = new ArrayList<>();
        for (InetAddress address : addresses) {
            if (address instanceof Inet4Address) {
                result.add(address);
            }
        }
        for (InetAddress address : addresses) {
            if (!(address instanceof Inet4Address)) {
                result.add(address);
            }
        }

        return result;
    }
}