Java连接mongodb报错了，，怎么解决?报错

Exception in thread "main" com.mongodb.CommandResult$CommandFailure: command failed [command failed [listDatabases] { "serverUsed" : "192.168.100.77:27017" , "ok" : 0.0 , "errmsg" : "not authorized on admin to execute command { listDatabases: 1 }" , "code" : 13}
    at com.mongodb.CommandResult.getException(CommandResult.java:75)
    at com.mongodb.CommandResult.throwOnError(CommandResult.java:121)
    at com.mongodb.Mongo.getDatabaseNames(Mongo.java:328)
    at com.fz.test.SimpleTest.main(SimpleTest.java:16)

package com.fz.test;

import java.net.UnknownHostException;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
import com.mongodb.util.JSON;

public class SimpleTest {
	public static void main(String[] args) throws UnknownHostException,
			MongoException {
		Mongo mg = new Mongo("192.168.2.77", 27017);
		// 查询所有的Database
		for (String name : mg.getDatabaseNames()) {
			System.out.println("dbName: " + name);
		}
		DB db = mg.getDB("test");
		// 查询所有的聚集集合
		for (String name : db.getCollectionNames()) {
			System.out.println("collectionName: " + name);
		}
		DBCollection users = db.getCollection("users");
		// 查询所有的数据
		DBCursor cur = users.find();
		while (cur.hasNext()) {
			System.out.println(cur.next());
		}
		System.out.println(cur.count());
		System.out.println(cur.getCursorId());
		System.out.println(JSON.serialize(cur));
	}
}