Mongodb 找不到要打印的收藏

我试图显示mongodb服务器的集合，但MongoController类在FindTable中查找集合时遇到困难。我相信这可能是一个语法错误，但我不明白是什么错了

MongoController类

import com.mongoDB.MongoDAO;
import org.bson.Document;

import com.mongodb.client.FindIterable;

public class MongoController {


    FindIterable<Document> mondgoDB = collection.find();


      for (Document d : users) {
        System.out.println(d.toJson());
      }

      mongoClient.close();

}

}

package com.mongoDB;

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

public class MongoDAO {

    String mongoDB = "storeHeadOfficeDB";
    String mongoCollection = "storeHeadOffice";


    public MongoDAO() throws Exception {
        MongoClient mongoClient = new MongoClient();
        MongoDatabase database = mongoClient.getDatabase(mongoDB);
        MongoCollection collection = database.getCollection(mongoCollection);
    }
}

mondgoDB = dbname.collection.find()