Java (HttpClient, OkHttp)

import java.net.InetSocketAddress;
import java.net.ProxySelector;
import java.net.Authenticator;
import java.net.PasswordAuthentication;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class ColdProxyExample {
    public static void main(String[] args) throws Exception {
        // Required for Basic proxy auth over HTTPS tunnels (see WARNING below)
        System.setProperty("jdk.http.auth.tunneling.disabledSchemes", "");
        System.setProperty("jdk.http.auth.proxying.disabledSchemes", "");

        String user = "USERNAME";
        String pass = "PASSWORD";

        HttpClient client = HttpClient.newBuilder()
            .proxy(ProxySelector.of(
                new InetSocketAddress("gw-2312.coldproxy.com", 30000)))
            .authenticator(new Authenticator() {
                @Override
                protected PasswordAuthentication getPasswordAuthentication() {
                    if (getRequestorType() == RequestorType.PROXY) {
                        return new PasswordAuthentication(user, pass.toCharArray());
                    }
                    return null;
                }
            })
            .build();

        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://api.vipv6proxy.com/api/checker/my-ip"))
            .build();

        HttpResponse<String> response =
            client.send(request, HttpResponse.BodyHandlers.ofString());
        System.out.println(response.body()); // JSON: {"ip": "...", "version": ..., ...}
    }
}

import java.net.InetSocketAddress;
import java.net.Proxy;
import okhttp3.Credentials;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class ColdProxyOkHttp {
    public static void main(String[] args) throws Exception {
        String user = "USERNAME";
        String pass = "PASSWORD";

        Proxy proxy = new Proxy(Proxy.Type.HTTP,
            new InetSocketAddress("gw-2312.coldproxy.com", 30000));

        OkHttpClient client = new OkHttpClient.Builder()
            .proxy(proxy)
            .proxyAuthenticator((route, response) -> {
                if (response.request().header("Proxy-Authorization") != null) {
                    return null; // already failed with these credentials: give up
                }
                String credential = Credentials.basic(user, pass);
                return response.request().newBuilder()
                    .header("Proxy-Authorization", credential)
                    .build();
            })
            .build();

        Request request = new Request.Builder()
            .url("https://api.vipv6proxy.com/api/checker/my-ip")
            .build();

        try (Response response = client.newCall(request).execute()) {
            System.out.println(response.body().string());
        }
    }
}

// Rotating US exit IP — confirm the exact country prefix in your client area
String user = "user-country-us";
String pass = "PASSWORD";

// Sticky US IP for 10 minutes — same session ID + duration reuses the exit IP
String user = "user-country-us-session-481516-time-10m";
String pass = "PASSWORD";

// IP-authenticated — no Authenticator needed
HttpClient client = HttpClient.newBuilder()
    .proxy(ProxySelector.of(
        new InetSocketAddress("gw-2312.coldproxy.com", 30000)))
    .build();