如何使用Java检查Google Cloud Storage中是否存在文件夹？

<dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>google-cloud-storage</artifactId>
    <version>版本号</version>
</dependency>

import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;

Storage storage = StorageOptions.getDefaultInstance().getService();

import com.google.cloud.storage.Blob;
import com.google.cloud.storage.BlobId;

String bucketName = "存储桶名称";
String folderName = "文件夹名称";

BlobId blobId = BlobId.of(bucketName, folderName);
Blob blob = storage.get(blobId);

if (blob != null && blob.isDirectory()) {
    System.out.println("文件夹存在");
} else {
    System.out.println("文件夹不存在");
}