http client buffer repro

gistfile1.txt

import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class HttpClientBufTest {
  static int LINES = 10_000;

  public static void main(String[] args) throws Exception {
    HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
    server.createContext("/test", new MyHandler());
    server.setExecutor(null); // creates a default executor
    server.start();

    Thread.sleep(1000);
    var request = HttpRequest.newBuilder(URI.create("http://localhost:8080/test")).GET().build();
    var httpClient = HttpClient.newHttpClient();
    var tempFile = Files.createTempFile("tempFile-", ".txt");
    try {
      httpClient.send(request, HttpResponse.BodyHandlers.ofFile(tempFile));

      boolean received[] = new boolean[LINES];
      Pattern p = Pattern.compile("This is line: (?<num>[0-9]+)");
      for (String line : Files.readAllLines(tempFile, StandardCharsets.UTF_8)) {
        Matcher matcher = p.matcher(line);
        if (matcher.matches()) {
          received[Integer.parseInt(matcher.group("num"))] = true;
        } else {
          System.out.println("Corrupted line received: " + line);
        }
      }

      for (int i = 0; i < received.length; i++) {
        if (!received[i]) {
          int j = i;
          while (j < received.length && !received[j]) {
            j++;
          }
          System.out.println("Missed line range: " + i + "-" + (j - 1));
          i = j;
        }
      }

    } finally {
      Files.delete(tempFile);
    }

    server.stop(0);
  }

  static class MyHandler implements HttpHandler {
    @Override
    public void handle(HttpExchange t) throws IOException {
      t.sendResponseHeaders(200, 0);
        try (OutputStream os = t.getResponseBody()) {
          for (int i = 0; i < LINES; i++) {
          String line = "This is line: " + i + "\n";
          os.write(line.getBytes(StandardCharsets.UTF_8));
          os.flush();
        }
      }
    }
  }
}