How to use a proxy with Java HttpClient

java -Djdk.http.auth.tunneling.disabledSchemes= -jar crawler.jar# or, first line of main():#   System.setProperty("jdk.http.auth.tunneling.disabledSchemes", "");

import java.net.Authenticator;import java.net.InetSocketAddress;import java.net.PasswordAuthentication;import java.net.ProxySelector;import java.net.URI;import java.net.http.HttpClient;import java.net.http.HttpRequest;import java.net.http.HttpResponse;import java.time.Duration;public class ExitIp {    static HttpClient arcClient(String username) {        return HttpClient.newBuilder()            .proxy(ProxySelector.of(new InetSocketAddress("proxy.arcproxies.io", 8000)))            .authenticator(new Authenticator() {                @Override                protected PasswordAuthentication getPasswordAuthentication() {                    if (getRequestorType() != RequestorType.PROXY) return null;                    return new PasswordAuthentication(username, "PASSWORD".toCharArray());                }            })            .connectTimeout(Duration.ofSeconds(10))            .build();    }    public static void main(String[] args) throws Exception {        System.setProperty("jdk.http.auth.tunneling.disabledSchemes", "");        HttpClient client = arcClient("USERNAME_pool-arcfast_country-de");        HttpRequest req = HttpRequest.newBuilder(URI.create("https://api.ipify.org?format=json"))            .timeout(Duration.ofSeconds(30))            .build();        HttpResponse<String> res = client.send(req, HttpResponse.BodyHandlers.ofString());        System.out.println(res.statusCode() + " " + res.body());    }}

// uses arcClient(...) from ExitIp.javaString handle = java.util.HexFormat.of().formatHex(java.security.SecureRandom.getSeed(4));String user = "USERNAME_pool-arcfast_country-de_session-" + handle + "_sesstime-10";try (HttpClient session = ExitIp.arcClient(user)) {    for (int page = 1; page <= 3; page++) {        HttpRequest req = HttpRequest.newBuilder(                URI.create("https://example.com/search?q=lamp&page=" + page))            .timeout(Duration.ofSeconds(30))            .build();        System.out.println(page + " " + session.send(req, HttpResponse.BodyHandlers.discarding()).statusCode());    }}

Map<String, String> markets = Map.of(    "de-frankfurt", "USERNAME_pool-arcfast_country-de_city-frankfurt",    "jp-nagoya",    "USERNAME_pool-arcfast_country-jp_city-nagoya",    "pl-warsaw",    "USERNAME_pool-arcfast_country-pl_city-warsaw");for (var m : markets.entrySet()) {    try (HttpClient c = ExitIp.arcClient(m.getValue())) {        HttpRequest req = HttpRequest.newBuilder(URI.create("https://example.com/price/123"))            .timeout(Duration.ofSeconds(30)).build();        System.out.println(m.getKey() + " " + c.send(req, HttpResponse.BodyHandlers.discarding()).statusCode());    }}

static HttpResponse<String> fetch(String url) throws Exception {    for (int attempt = 0; attempt < 4; attempt++) {        String handle = java.util.HexFormat.of().formatHex(java.security.SecureRandom.getSeed(4));        try (HttpClient c = ExitIp.arcClient("USERNAME_pool-arcfast_country-de_session-" + handle + "_sesstime-5")) {            HttpRequest req = HttpRequest.newBuilder(URI.create(url)).timeout(Duration.ofSeconds(30)).build();            HttpResponse<String> res = c.send(req, HttpResponse.BodyHandlers.ofString());            if (res.statusCode() == 407) {                throw new IllegalStateException("407: check disabledSchemes and the credentials");            }            if (res.statusCode() != 429 && res.statusCode() < 500) return res;        } catch (java.net.http.HttpTimeoutException e) {            // new exit on the next attempt        } catch (java.io.IOException e) {            if (String.valueOf(e.getMessage()).contains("authentication attempts")) throw e;        }        Thread.sleep(1000L << attempt);   // 1 s, 2 s, 4 s, 8 s    }    throw new IllegalStateException("gave up on " + url);}