如何在Java中遍历firestore中的列表列表？

import com.google.cloud.firestore.Firestore;
import com.google.cloud.firestore.FirestoreOptions;

// 初始化Firestore实例
FirestoreOptions firestoreOptions = FirestoreOptions.getDefaultInstance().toBuilder()
    .setProjectId("your-project-id")
    .build();
Firestore firestore = firestoreOptions.getService();

import com.google.cloud.firestore.CollectionReference;
import com.google.cloud.firestore.DocumentSnapshot;
import com.google.cloud.firestore.QueryDocumentSnapshot;
import com.google.cloud.firestore.QuerySnapshot;

// 获取集合引用
CollectionReference usersCollection = firestore.collection("users");

// 获取集合中的所有文档快照
QuerySnapshot querySnapshot = usersCollection.get().get();

// 遍历每个文档快照
for (QueryDocumentSnapshot documentSnapshot : querySnapshot.getDocuments()) {
    // 从文档快照中提取数据
    String userId = documentSnapshot.getId();
    String userName = documentSnapshot.getString("name");
    int userAge = documentSnapshot.getLong("age").intValue();

    // 打印提取的数据
    System.out.println("User ID: " + userId);
    System.out.println("User Name: " + userName);
    System.out.println("User Age: " + userAge);
}