如何使用MongoDB和Java在返回语句中不使用循环来检索特定字段？

import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;

import java.util.Arrays;

public class MongoDBExample {
    public static void main(String[] args) {
        // 连接MongoDB数据库
        MongoClient mongoClient = MongoClients.create("mongodb://localhost:27017");
        MongoDatabase database = mongoClient.getDatabase("mydb");
        MongoCollection<Document> collection = database.getCollection("mycollection");

        // 创建聚合管道
        Document matchStage = new Document("$match", new Document("field", "value"));
        Document projectStage = new Document("$project", new Document("field", 1));
        Document pipeline = new Document("$pipeline", Arrays.asList(matchStage, projectStage));

        // 执行聚合查询
        Document result = collection.aggregate(Arrays.asList(pipeline)).first();

        // 获取特定字段的值
        String fieldValue = result.getString("field");
        System.out.println("Field value: " + fieldValue);
    }
}