Loading CSS from a URL in Java with OkHTTP

import okhttp3.*;
import java.io.IOException;

// You can get an API key at https://pdfshift.io
String apiKey = "sk_xxxxxxxxxxxx";

OkHttpClient client = new OkHttpClient();

RequestBody body = RequestBody.create(
    "{\n" +
    "  \"source\": \"https://www.example.com\",\n" +
    "  \"css\": \"https://example.com/styles.css\"\n" +
    "}", MediaType.parse("application/json"));

Request request = new Request.Builder()
    .url("https://api.pdfshift.io/v3/convert/pdf")
    .addHeader("X-API-Key", apiKey)
    .post(body)
    .build();

try (Response response = client.newCall(request).execute()) {
    
    // Handle errors:
    if (!response.isSuccessful()) {
        throw new IOException("Request failed with status code " + response.code());
    }
    
    ResponseBody responseBody = response.body();
    if (responseBody != null) {
        java.nio.file.Files.write(
            java.nio.file.Paths.get("result.pdf"), 
            responseBody.bytes()
        );
    }
    
    System.out.println("The PDF document was generated and saved to result.pdf");
}