How can I speed up the query time for the server in Java?

I need to make 700 requests for various json. For example, if I make one of these requests, the response takes 12 seconds. Accordingly, all 700 requests will take about 2 hours.

I used the HtmlUnit libraries (net.sourceforge.htmlunit) and rest-assured (com.jayway.restassured)

Example code on HtmlUnit for two queries:

WebClient client = new WebClient();
Page page = client.getPage("https://api.privatbank.ua/p24api/exchange_rates?json&date=01.12.2014");
WebResponse response = page.getWebResponse();

Page page2 = client.getPage("https://api.privatbank.ua/p24api/exchange_rates?json&date=02.12.2014");
WebResponse response2 = page2.getWebResponse();

System.out.println(response.getContentAsString());
System.out.println(response2.getContentAsString());

Example code on rest-assured for two requests:

String sURL ="https://api.privatbank.ua/p24api/exchange_rates?json";
Map<String, String> queryParms= new HashMap<>();
queryParms.put("date", String.valueOf("01.12.2014"));
Response response =  RestAssured.expect().statusCode(200).given()
        .queryParameters(queryParms)
        .log().all()
        .when()
        .get(sURL)
        .then().assertThat()
        .log().all()
        .extract().response();
System.out.println(response.getBody().asString());

queryParms.put("date", String.valueOf("02.12.2014"));
Response response =  RestAssured.expect().statusCode(200).given()
        .queryParameters(queryParms)
        .log().all()
        .when()
        .get(sURL)
        .then().assertThat()
        .log().all()
        .extract().response();
System.out.println(response.getBody().asString());

On the other hand, if I make a request through the browser to the same addresses, for example via Chrome, then the request occurs instantly.

How on Java do the same fast queries?