Mongodb java api WriteResult#getN()

使用Mongodb Java API的WriteResult#getN()方法可以获取Mongodb数据库中写操作的结果数量。该方法返回一个整数，表示写操作影响的文档数量。在本文中，我们将介绍WriteResult#getN()方法的使用，并提供一个案例代码来说明其功能。

java
import com.mongodb.*;
public class WriteResultExample {
    public static void main(String[] args) {
        MongoClient mongoClient = new MongoClient("localhost", 27017);
        DB database = mongoClient.getDB("mydb");
        DBCollection collection = database.getCollection("mycollection");
        // 插入文档
        BasicDBObject document = new BasicDBObject();
        document.put("name", "John Doe");
        document.put("age", 30);
        WriteResult writeResult = collection.insert(document);
        int n = writeResult.getN();
        System.out.println("插入了 " + n + " 个文档");
        // 更新文档
        BasicDBObject query = new BasicDBObject();
        query.put("name", "John Doe");
        BasicDBObject update = new BasicDBObject();
        update.put("$set", new BasicDBObject("age", 35));
        writeResult = collection.update(query, update);
        n = writeResult.getN();
        System.out.println("更新了 " + n + " 个文档");
        // 删除文档
        query = new BasicDBObject();
        query.put("name", "John Doe");
        writeResult = collection.remove(query);
        n = writeResult.getN();
        System.out.println("删除了 " + n + " 个文档");
        mongoClient.close();
    }
}