以下是使用 jloop AsyncHttpClient 检查外部文件是否存在的解决方法的示例代码。

Kotlin 示例：

import com.jloop.http.async.AsyncHttpClient
import kotlinx.coroutines.runBlocking
import java.io.File

fun main() {
    val url = "https://example.com/file.txt"
    val filePath = "/path/to/file.txt"

    val client = AsyncHttpClient()
    val request = client.get(url)

    val response = runBlocking {
        client.execute(request)
    }

    if (response.statusCode == 200) {
        val file = File(filePath)
        if (file.exists()) {
            println("File exists")
        } else {
            println("File does not exist")
        }
    } else {
        println("Failed to download file")
    }
}

Java 示例：

import com.jloop.http.async.AsyncHttpClient;
import com.jloop.http.async.Response;
import java.io.File;

public class Main {

    public static void main(String[] args) {
        String url = "https://example.com/file.txt";
        String filePath = "/path/to/file.txt";

        AsyncHttpClient client = new AsyncHttpClient();
        AsyncHttpClient.Request request = client.get(url);

        Response response = client.execute(request).join();

        if (response.getStatusCode() == 200) {
            File file = new File(filePath);
            if (file.exists()) {
                System.out.println("File exists");
            } else {
                System.out.println("File does not exist");
            }
        } else {
            System.out.println("Failed to download file");
        }
    }
}

请注意，上述示例代码仅演示了检查文件是否存在的基本逻辑，您可能需要根据自己的需求进行适当的修改和优化。