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winter holiday是什么意思

一、winter holiday的意思是:寒假二、例句: 1.What are going to do this winter holiday? 今年寒假你想做什么事情?2. Will you go back to your hometown for Spring Festival this winter holiday? 你今年寒假会回家乡过年吗?

be separated from 与be separated into的区别?

前者是与某物分开的意思。 后者是分为,分解为的意思

be divided into和be separated by 区别是什么?

前者是把一个东西一个东西分类 就着是把整体东西分开

federally-guaranteed是什么意思

federally-guaranteed政府保证双语对照例句:1.That meant moving into higher-quality bonds, such as investment-grade corporate andtreasurys, as well as federally-guaranteed bank certificates of deposit. -----------------------------------如有疑问欢迎追问!满意请点击右上方【选为满意回答】按钮

separated into可造句造为separated sth into...,吗?

可以。1、separate既是及物动词,也是不及物动词。2、确实有separated sth into...的用法。如:He has separated the wood-log into pieces.他将那块木头劈得粉碎。

separate from和divide into的区别

separate from 把一堆东西的一部分分出来.比如说,把一堆苹果中的烂苹果挑出来. divide into 把一个整体分开.比如说,把一个蛋糕切开. 扩展资料   例句:   Is it possible to separate truth from fiction?   有可能把事实与虚构分开吗?   It was absolutely essential to separate crops from the areas that animals used as pasture   将庄稼和放牧区分开绝对必要。   The Trust needs a new law to divide it up into smaller bodies.   该托管组织需要有新法律来将它分成若干小型机构。   Divide the dough into 12 even pieces and shape each piece into a ball   将面团分成12等份,每份揉成球状。

USA-city,county,state,federal之间的关系和区别

city是城市,比如说像北京那种 county是乡村,这在我国多的是, state是州 ,比如说堪萨斯州,federal是联邦

My winter holiday80词左右

寒假趣事(happy winter holiday) I have got a happy winter holiday this year. In this year, I have a 7-day winter holiday. In the first day, I went back to my hometown with my parents. When I got there, I saw my grandparents. Then we had lunch together. At that time, we not only had dilicious food,we also talk about our wonderful life. We laughed and sang, it was so happy then. After lunch, I got out and found my old friends in the field. They were all taller and stronger than before. We sat down on the ground and talk about funny things. It was so interesting and fun. We also played some funny games. I have never play such a funny game since I leave my hometown for a big city. I was so happy that day.It was the happiest time in my holiday. And it was so funny. 我的快乐寒假(My happy winter holiday) I have a busy holiday, On weekend, I clean the room ,I play the computer game ,and I do my homework. Another day ,I have a big trip ,It"s nice! I visit my grandparents now, I eat good food, drink Cock,and I sing vevy nice.My grandparents are very happy. I think, too. What about you? what are you going to do on the winter holiday? My Winter Holiday I have a happy winter holiday, because I go to many places. First, I go to Liannan to climb mountains and visit some old houses. Then I go to Longmen. In the evening, we go to the hot spring. My mother"s friend says, "There are many squirrels in Nankun mountain!" That"s very interesting! I want to see monkeys very much. But we don"t have time to go there. I am so sad! Later, we go to other places, such as Xi Qiao, Guangzhou, etc. I love my colourful winter holiday! What about your holiday? 快乐的寒假(Happy winter holiday) Oh, yeah! Happy winter holiday! I"ve been back home already, watching TV, watching American movies, Japanese movies and cartoons and every thing! Bon appetite for my breakfast and lunch at home. Every thing at home is good to me. I love my kind grandma and grandpa, my daddy and mummy, cousins, aunts and uncles and all of my relatives. However, a promising future is always around the corner as long as I do prepare for it. Come on, baby! 就给你这么多了。自己选个合适的。 rainbowolf8183 抄人家的不对哦

federal government是什么意思

联邦政府……

MONT BLANC钢笔的英文介绍

Montblanc  万宝龙(Mont Blanc),1906年在德国汉堡由一位文具商创立创建,在1911年采纳万宝龙的商标前该公司以Simplo Filler Pen Company的名字成立。该公司后来由登喜路所有而现时为历峰集团形式上的一部份。 近一个世纪以来,万宝龙(Mont Blanc)以制造经典书写工具驰名于世,万宝龙的名号代表着书写的艺术,笔顶的六角白星标记,恰恰是欧洲最高的山峰勃朗峰俯瞰的形状,象征着欧洲最高山峰勃朗峰(Mont Blanc)的雪岭冠冕, 该山峰的最高点为海拔4810米,而每支笔尖上的“4810”字样正是勃朗峰的高度,该数字通常偱环用作各种主题。而纯手工制作、经过25道工序打造的笔头,更使得MONT BLANC书写工具如勃朗峰般坚实而又高贵。创始人:Alfred Nehemias, August Eberstein, Claus-Johannes Voss  年代:1906年  国家:德国  所属机构:历峰集团  官方网站: http://www.montblanc.com

his parents separated为什么要用被动?

应该不是被动语态哦这里的separated 是单独行动的 前面没有加be动词所以只是表达了过去就分开的意思一种过去的时态

These dolls represent a royal family in Japan about ()years ago, in Heian period.()

These dolls represent a royal family in Japan about ()years ago, in Heian period.() A.13,000 B.300 C.1,300 D.1000 正确答案:C

fequently造句

fequently 没有这儿词

talent show的汉语翻译。

具体的翻译如下:Everyone is good at something, but some people do have talent. It"s always fun to watch others show their talents. Talent shows are becoming more and more popular.每一个人都有擅长的事,但是有些人确实有天赋。观看别人展示他们的才艺总是有趣的。才艺展示越来越受欢迎。At first, there were talent shows such as American Idol and American talent show. Now, there are similar performances all over the world, such as China"s got talent show.刚开始,有像《美国偶像》和《美国达人秀》这样的才艺表演。现在,世界各地都有类似的表演,像 《中国达人秀》。All these performances have the same characteristic: they try to find the best singers, the most talented dancers, the most exciting magicians, the funniest actors and so on.所有的这些表演都有一个相同的特点:他们尽量地寻找最优秀的歌手、最有天赋的舞者、最令人兴奋的魔术师、 最滑稽的演员等等。 All kinds of people can participate in these performances. But who can play the piano best or sing best? It"s up to you.各种各样的人都可参加这些表演。但是谁能把钢琴弹得最好或者歌唱得最好听呢? 那由你决定。When people are watching a show, they usually play a role in determining the champion. And the winner can always get a very good prize.当人们现看表演时,他们通常发挥决定冠军的作用。而且获胜者总是能够得到一份非常不错的奖品。

frenquently, all the time,everym

事实是我时刻都很想你。每秒,每分钟,每小时,每天。

fluquently是什么意思的翻译是:什么意思

题主单词错误,应该是frequently吧。frequent的副词,频繁地

求雅思口语part1关于Concentrating问题及答案 具体内容: What times i

下面是根据我自己的情况写的,最好结合你自己的情况否则考官追问对不上怀疑背答案会扣分,本人口语只有6. 5对话中不擅长用高级词汇和句型但是习惯答得很多,希望能帮到你:1. Well, as a high school student, I was frenquently told to concentrate on my study before big exams, like this IELTS test, final exams and the high school entrance exam. Those days could be very fast-paced cuz I hardly have any leisure.2. Yeah. Some subjects like maths requires not only concentrating on details buy also great patience when caculating. Also, when I am reading an article from textbook, misunderstanding of a single word might lead to many faults.3. I suppose it"s depend on the surroundings. When the classroom is very noisy and all the classmates around me are chatting, it could be hard for me to pay attention to my homework and I hate to be disturbed when I am concentrating on something. Howerver, I can concentrate easily when I listen to soft music or sit in a quite place.4和5. (参照第三题回答)6.As for me, I can say that I can"t leave my ipod and my headphone. I get used to listen to soft music when I am studying. Some people may find this habbit ridiculous and detrimental to my ability of concentrating, but I am not in agreement with them, or I would get bored soon.7. (参照第6题) It depends on the situation. My habbit is to listen to soft music when studying because it helps me to keep myself intrested to what I am doing, however it would be a bad idea to watching TV when reading a book. What I mean is that one person is able to do two different things on the premise that one thing he is doing will not disturb his concentrating on another thing.临时写得没有仔细看过,语法拼写错误你自己再看看,望采纳!

im going to use it prequently是什么意思

im going to use it frequently我会频繁地使用它

country怎么读

country的读音是:英["k?ntri]。country的读音是:英["k?ntri]。country的详尽释义是n.(名词)国,国家,祖国国土,土地故乡区域,地区乡下,乡村全体国民,全国人民,国民,全民郊外领域政府。country名词复数:countries。一、详尽释义点此查看country的详细内容n.(名词)国,国家,祖国国土,土地故乡区域,地区乡下,乡村全体国民,全国人民,国民,全民郊外领域政府adj.(形容词)乡下的,乡村的,农村的,乡间的乡村风味的,乡村式的,乡气的故乡的,家乡的地方的粗鲁的祖国的,本国的,本土的,本地的【音】乡村音乐的,以乡村音乐为特色的在农村的,来自农村的二、英英释义Noun:a politically organized body of people under a single government;"the state has elected a new president""African nations""students who had come to the nation"s capitol""the country"s largest manufacturer""an industrialized land"the territory occupied by a nation;"he returned to the land of his birth""he visited several European countries"the people who live in a nation or country;"a statement that sums up the nation"s mood""the news was announced to the nation""the whole country worshipped him"an area outside of cities and towns;"his poetry celebrated the slower pace of life in the country"a particular geographical region of indefinite boundary (usually serving some special purpose or distinguished by its people or culture or geography);"it was a mountainous area""Bible country"三、词典解释1.国;国家Acountry is one of the political units which the world is divided into, covering a particular area of land.countrye.g. Indonesia is the fourth most populouscountry in the world.印度尼西亚是世界上第四大人口大国。e.g. ...that disputed boundary between the two countries...两国之间存有争议的边境地区2.全国人民;国民;全民The people who live in a particular country can be referred to asthe country .e.g. Thecountry had confounded the pundits by electing a fourth-term Tory government...该国国民连续四次选举托利党来执掌政府,这令专家们困惑不已。e.g. Seventy per cent of thiscountry is opposed to blood sports.该国70%的人反对猎兽活动。3.乡下;乡村The country consists of places such as farms, open fields, and villages which are away from towns and cities.e.g. ...a healthy life in thecountry...乡下的健康生活e.g. She was cycling along acountry road near Compiegne...她正骑车行进在贡比涅附近的乡村道路上。4.(具有某种特征或与某名人有关的)地区,区域A particular kind ofcountry is an area of land which has particular characteristics or is connected with a particular well-known person.e.g. Varese Ligure is a small town in mountainouscountry east of Genoa.瓦雷泽古雷是位于热那亚以东山区的一座小城。e.g. ...some of the best walkingcountry in the Sierras...喜艾拉生态保护区内一些最适宜散步的地区5.(源自美国南部的)乡村音乐Country music is popular music from the southern United States.e.g. For a long time I just wanted to playcountry music.有很长一段时间我只想弹奏乡村音乐。e.g. ...a famouscountry singer named Katie Cocker.一位名为凯蒂·科克尔的著名乡村乐歌手6.穿过田野;不走大路If you travelacross country, you travel through country areas, avoiding major roads and towns.e.g. From here we walked acrosscountry to Covington.我们从这儿走乡间小路去卡温顿。7.长途;长距离;跨越地区地If you travelacross country, you travel a long distance, from one part of a country to another.e.g. We"ve just moved all the way acrosscountry to begin a new life.我们刚刚经过长途的搬迁来这里开始一种新生活。8.(政府首脑或政府)举行大选If a head of government or a governmentgoes to the country, they hold a general election.e.g. The Prime Minister does not have to go to thecountry for another year.首相明年也不用举行大选。Country is the most usual word to use when you are talking about the major political units that the world is divided into.State is used when you are talking about politics or government institutions....the new German state created by the unification process. ...Italy"s state-controlled telecommunications company.State can also refer to a political unit within a particular country....the American state of California.Nation is often used when you are talking about a country"s inhabitants, and their cultural or ethnic background.Wales is a proud nation with its own traditions... A senior government spokesman will address the nation.Land is a less precise and more literary word, which you can use, for example, to talk about the feelings you have for a particular country.She was fascinated to learn about this strange land at the edge of Europe.当谈论世界所划分成的主要政治单位时, country 最为常用,当谈论政治或政府组织时用 state。例如,the new German state created by the unification process (统一后成立的新德国),Italy"s state-controlled telecommunications (意大利由国家控制的电信公司)。state 还可指某国国内的行政单位,例如,the American state of California (美国加利福尼亚州)。当谈论某国的居民及其文化或种族背景时常用 nation。例如:Wales is a proud nation with its own traditions (威尔士是一个拥有自己传统的自豪的民族),A senior government spokesman will address the nation (一位政府高级发言人将发表全国讲话)。land 含义较为笼统而文学意味更浓,可用来谈论对某国的感情等。例如,She was fascinated to learn about this strange land at the edge of Europe (她非常渴望了解这个位于欧洲边缘的奇异国度)。四、例句China is a developing country.中国是一个发展中国家。After many years abroad, he wanted to return home to his country.在国外多年后,他想回到故乡。The country is very green in spring.春天的时候,乡村一片青葱碧绿。She lived her whole life in the country.她在农村度过一生。We passed through miles of wooded country.我们通过了好几英里的树木茂密的地带。This is unknown country to me.我以前没到过这里/我对这问题一窍不通。After ten years in the city, he is still country.他在城里待了十年,仍是乡气十足。I strictly criticize those country leaders who advocate crossover.我强力谴责鼓吹跨党派投票的国家领导。五、常见句型用作名词(n.)Our country is becoming stronger and stronger.我们的国家日益强大。Their country has democratic government.他们国家实行民主政体。The country is importing a broad range of skilled personnel.这个国家正在引进各行各业的技术人员。That country"s foreign exchange reserves are falling.那个国家的外汇储备正在减少。They will visit the country again at a proper time.他们将在适当的时候再度访问这个国家。The fuel shortage awoke the country to the need for developing atomic energy.燃料匮乏使这个国家认识到开发原子能的必要性。He was bent to make his country prosperous and people happy.他立意要使自己的祖国繁荣,人民幸福。His fame was blazed abroad by the country"s newspapers and television.通过国内报纸和电视的宣传,他名扬天下了。Vast new oilfields have been discovered in our country.在我国发现了许多巨大的新油田。Short sight is less common among the young students in this country.近视在这个国家的青年学生中较为少见。Huge changes have happened in this country from 1980 to 1990.从1980年到1990年这个国家发生了巨大变化。The military has tightened its hold on the country.军方加强了对国家的控制。I believe this will add greatly to our understanding of your country.我相信这次到这里来将大大加深我们对贵国的了解。What they did ill accords with the interests of this country.他们所做的事情不符合国家的利益。When you go to a new country, you must adapt yourself to new manners and customs.当你到一个新的国家时,你必须使自己适应新的风俗习惯。The country is bracing itself for the threatened enemy invasion.这个国家正准备奋起抵抗敌人的入侵威胁。The whole country turned out to celebrate the holiday.全国人民都参加节日的庆祝活动。We travelled across country.我们走在田野上。The river broke through its banks, and flooded the country for many miles around .河水决堤,淹没了方圆许多英里的乡村。We hope to move to the country in the near future.我们希望在不久的将来移居乡下。They are just simple country folk.他们只不过是普通的村民。Peacefulness is one of the delights of country life.宁静是乡村生活的乐处之一。The small town was surrounded by rolling country.小镇四周都是丘陵地带。We passed through miles of wooded country.我们经过了大片的森林地带。六、经典引文A country of gracious farms on undulating hilly slopes.出自:N. Shute七、词源解说☆ 13世纪中期进入英语,直接源自古法语的contree;最初源自中古拉丁语的contrata,意为在那边的国土。country的相关近义词nation、state、countryside、villagecountry的相关反义词city、towncountry的相关临近词countryside、countless、country PE、countrymen、countryman、countrycode、country law、country inn、countrywide、countryseat、country pub、countryfied点此查看更多关于country的详细信息

报错:当前标识(NT AUTHORITYNETWORK SERVICE)没有写访问权限

打开vs时,右键管理员身份运行

有关authentication order dot1x mab

在考secie?

CENTOS 下启动qtcreat时报错,求教

QByteArray ProjectExplorer::runGcc(const Utils::FileName&, const QStringList&, const QStringList&): "/usr/local/bin/g++" "-xc++ -E -v -" returned exit code 1: "Using built-in specs.COLLECT_GCC=/usr/local/bin/g++Target: x86_64-unknown-linux-gnuConfigured with: ./configure --disable-multilibThread model: posixgcc version 4.9.1 (GCC) COLLECT_GCC_OPTIONS="-E" "-v" "-shared-libgcc" "-mtune=generic" "-march=x86-64" /usr/local/libexec/gcc/x86_64-unknown-linux-gnu/4.9.1/cc1plus -E -quiet -v -D_GNU_SOURCE - -mtune=generic -march=x86-64/usr/local/libexec/gcc/x86_64-unknown-linux-gnu/4.9.1/cc1plus: error while loading shared libraries: libmpc.so.3: cannot open shared object file: No such file or directory"QByteArray ProjectExplorer::runGcc(const Utils::FileName&, const QStringList&, const QStringList&): "/usr/local/bin/g++" "-xc++ -E -dM -D_REENTRANT -" returned exit code 1: "/usr/local/libexec/gcc/x86_64-unknown-linux-gnu/4.9.1/cc1plus: error while loading shared libraries: libmpc.so.3: cannot open shared object file: No such file or directory"

creat my account什么意思

应该是Create my account 表示 建立我的帐户

《TwentyThousandLeaguesUndertheSea》pdf下载在线阅读,求百度网盘云资源

《Twenty Thousand Leagues Under the Sea》(Verne, Jules)电子书网盘下载免费在线阅读资源链接:链接:https://pan.baidu.com/s/1mC7npN1g4vD2y8q6pWwo9A 提取码:fiav书名:Twenty Thousand Leagues Under the Sea作者:Verne, Jules出版社:Naval Inst Pr出版年份:1993-9页数:416内容简介:For the past 120 years, readers of English have known only a poor imitation of Jules Verne"s classic French novel Vingt Mille Lieues Sous les Mers and consequently relegated the writer to the category of a "boy"s author." Since 1873 the standard English version has been Lewis Mercier"s mangled "translation," a work that"s filled with errors, mistranslations, and bogus additions, and missing nearly a quarter of Verne"s original text.Now, thanks to the life-long efforts of two Verne scholars, the English-speaking world at last has access to a definitive translation, the only English version based solely on the level of literary artist and scientific visionary, a category he has always enjoyed in Europe and Russia.Mercier"s act of literary vandalism went unnoticed until 1965, when New York University English professor Walter Miller discovered the missing text and began the restoration of the Verne masterpiece. After nearly thirty years of work, including rigorous examinations of his translation by experts in marine technology and biology, Miller teamed that Frederick Paul Walter in 1992 to create this landmark scientific and literary achievement.Restored to the volume along with the original woodcut illustrations are the entertaining and often prescient drams of Captain Nemo, widely considered the prototypical science-fiction character. In this novel alone Verne has anticipated submarine diving planes, scuba gear, underwater laboratories, and marine ecological disasters. He also inspired large-scale underwater mining and farming of flora and fauna, and electricity from thermoclines, all currently in development.Restoration of these visionary ideas and some twenty-three percent of the original text is certain to elevate Verne"s standing in American scientific and literary circles.

意利delonghi咖啡机放了豆却打不出咖啡,然后显示一排英文,看不懂!怎么办?fill deanscontaitner

你把豆子放错地方啦。。。

create和invente有什么区别?

creat是创新,是在一个本来就存在的事物上在创出新的东西,如创新科技等invent意为发明创造,指创出一个原来不存在的事物,如发明灯泡、发明火箭

主坐标分 percent variation explained 是什么意思

percent variation explained %变异解释例句:1.Some variation may be explained by tax rates and the cost of real estate, wages and transport. 一些价格差异也许是由于税率,房地产价格,工资以及运输的不同造成。2.The total model had an adjusted r2 of 0.721, suggesting that the majority of variation in tar could be explained by the included parameters. 整个模型调整后的r2为0.721,说明焦油排放量的变化很大程度上可以用所包含的参数加以解释。3.Almost 90% of the variation in the positions of leading english teams is explained by wage bills. 英国顶尖球队联赛排名的变化几乎有90%源于球员薪水变化。

help me to explain a sentence

fact后面的that从句是同位语从句,in which引导的是定语从句。

gelee fondante是什么意思

glee fondante吉利软糖glee[英][gli:][美][ɡli]n.快乐,欢喜; 重唱的歌曲; [乐]合唱曲; 复数:gleesfondanten.软糖

USBCANii通过USB接口连接到电脑,使用周立功测试软件ZLGCANtest.exe,提示“打开设备失败”

检查驱动是否装好,即设备SYS要亮绿灯才是装好;设备类型是否选对。

用周立功pci5121卡时,装好了驱动,然后准备用zlgcantest测试,但是打开设备时显示打开设备失败,有没有人

1.确认一下设备管理器里面的驱动是否装好,即没有黄色问号和感叹号;2.电脑是否只装1张PCI-5121,因为装2张以上,要将索引号加1;3.是否有应用程序占用这张PCI-5121(即已经运行了程序);4.PCI-5121卡损坏;另外一个注意点:确认电脑为单核CPU,因为PCI-5121对于双核以上电脑支持不好,目前已经停产,接替其的智能卡为PCI-5010-U和PCI-5020-U(目前由于新智能卡还未销售,故一般都是用PCI-9820I,单双核都可以用);

如何兼容使用周立功CANTest软件

可以使用通用的USBCAN分析仪来连接设备,USBCAN-II Pro支持兼容它们的软件

大众santara是什么车?

小编就关于“大众santara是什么车?”为你提供以下相关内容:大众santara是桑塔纳汽车,桑塔纳(SANTANA)牌轿车是德国大众汽车公司在美国加利福尼亚州生产的品牌车,旗下车型有:桑塔纳87、桑塔纳2000、桑塔纳3000、桑塔纳vista志俊、全新桑塔纳等。大众汽车公司是一家总部位于德国沃尔夫斯堡的汽车制造公司,由费迪南德保时捷于1937年3月28日成立,公司旗下有奥迪、大众等品牌。大众车标像是由三个用中指和食指作出的v组成,表示大众公司及其产品必胜。

印度美少女歌手Rossa的歌曲《ayat ayat cinte》的歌词(印度语+中文译音)

Rossa的歌曲《ayat ayat cinte》的歌词: Desir pasir di padang tandus Segersang pemikiran hati Terkisah ku di antara cinta yang rumit Bila keyakinanku datang Kasih bukan sekadar cinta Pengorbanan cinta yang agung Ku pertaruhkan reff: Maafkan bila ku tak sempurna Cinta ini tak mungkin ku cegah Ayat-ayat cinta bercerita Cintaku padamu Bila bahagia mulai menyentuh Seakan ku bisa hidup lebih lama Namun harus ku tinggalkan cinta Ketika ku bersujud Bila keyakinanku datang Kasih bukan sekedar cinta Pengorbanan cinta yang agung Ku pertaruhkan repeat reff Ketika ku bersujud希望你喜欢!!!

2015英语二,text2,翻译一句话,长难句,how to deal with the issues that face most college students.

如何应对摆在他们(大学生)大多数人面前的问题

account verification是什么意思

验证你的账户;帐户验证;新会员电邮验证例句Allaccountopeningprocessincludingaccountverificationmustbeperformedbytheaccountowner.所有的开户帐号的验证过程中,都必须履行由账户拥有者进行验证

antara是什么车?

安塔拉是欧宝,欧宝(OPEL,Op)是美国通用汽车的子公司,成立于1862年。这家公司首先生产缝纫机和自行车,然后开始生产汽车。1931年,它成为通用汽车在德国的子公司。作为欧洲最畅销的品牌之一,欧宝纯正优秀的德国技术深入人心,为大家所熟知。未来,欧宝的创新性、灵活性和多样性将在其全新形象的照耀下发扬光大,其无限的动感和卓越的品质将带给人们更新鲜、更自信的驾驶体验和汽车文化。

account verification是什么意思

验证你的账户;帐户验证;新会员电邮验证例句All account opening process including account verification must be performed by the account owner.所有的开户帐号的验证过程中,都必须履行由账户拥有者进行验证

anti-bot verification什么意思

意思是 反外挂验证

If winter comes,can spring be far away?的原文是什么?

1 O wild West Wind, thou breath of Autumn"s being Thou, from whose unseen presence the leaves dead Are driven, like ghosts from an enchanter fleeing, Yellow, and black, and pale, and hectic red, Pestilence-stricken multitudes:O thou Who chariltest to their dark wintry bed The winged seeds, where they lie cold and low, Each like a corpse within its grave, until Thine azure sister of the Spring shall blow Her clarion o"er the dreaming earth, and fill (Driving sweet buds like flocks to feed in air) With living hues and odors plain and hill: Wild Spirit, which art moving everywhere; Destroyer and presserver; hear, oh, hear! 2 Thou on whose stream, "mid the steep sky"s commotion, Loose clouds like earth"s decaying leaves are shedd, Shook from the tangled boughs of Heaven and Ocean, angels of rain and lightning:there are spread On the blue surface of thine airy surge, Like the bright hair uplifted from the head Of some fierce Maenad, even from the dim verge Of the horizon to the Zenith"s height, The locks of the approaching storm.Thou dirge Of the dying year, to which this closing night Will be the dome of a vast sepulchre, Vaulted with all thy congregated might Of vapoursr, from whose solid atmosphere Black rain, and fire , and hail will burst :oh, hear! 3 Thou who didst waken from his summer dreams The blue Mediterranean, where he lay, Lulled by the coil of his crystalline streams Beside a pumice isle in Baiae"s bay, And saw in sleep old palaces and fowers Quivering within the eave"s intenser day, All overgrown with azure moss and flowers So sweet, the sense faints picturing them!Thou For whose path the Atlantic"s level powers Cleave themselves into chasms, while far below The sea-blooms and the oozy woods which wear The sapless foliage of the ocean, know Thy voice, and suddenly grow gray with fear, And tremble and esepoil themselves:oh, hear! 4 If I were a dead leaf thou mightest bear; If I were a swift cloud to fly with thee: A wave to pant beneath thy power , and share The impulse of thy strength, only less free Than thou, O uncontrollable! If even I were as im my boyhood, and could be The comrade of thy wanderigs over Heaven, As then, when to outstrip thy skiey speed Scarce seem"d a vision; I would ne"er have striven As thus with thee in prayer in my sore need. Oh, lift me as a wave , a leaf, a cloud! I fall upon the thorns of life! I bleed! A heavy weight of hours has chained and bowed One too lke thee: tameless, and swift, and proud. 5 Make me thy lyre, even as the forest is: What if my leavers are falling like its own! The tmult of thy mighty harmonies Will take from both a deep, autumnal tone, Sweet though in sadness. Be thou, Spirit fierce, My spirit! Be thou me, impetuous one! Drive my dead thoughts over the universe Like witheered leaves to quicken a new birth! And , by the incantation of this verse, Scatter, is from an unextinguished hearth Ashes and sparks, my words among mankind! Be through my lips to unawakened earth The trumpet of a prophecy! O Wind, If Winter comes , can Spring be far behind?

USBCAN-II由USB口连后电脑,用周立功测试软件CANtest.exe,一直是“打开设备失败”,这是怎么了?

计算机系统也都是一样吗?或许的不兼容不配套吧

verification和authentication的区别?

基本一致。authentication更强调“身份”认证

santa monica这首歌要表达的是什么意思

是写给他离婚的妻子的,有说是批判所谓的时髦社会的。到底啥意思,估计只有写歌的人自己知道了。。Santa MonicaIn Santa Monica, in the winter time, 在圣塔 莫尼卡,在冬季 The lazy streets so undemanding 懒散的街道是如此的纵容 I walk into the crowd 我走进人群 In Santa Monica, you get your coffee from The coolest places on the promenade 在圣塔 莫尼卡,你从舞会最寒冷的地方拿着你的咖啡 Where people dress just so 那里人们穿着如此迷人 Beauty so unavoidable, everywhere you turn Its there 你转身的每个地方,就是那里 I sit and wonder what am I doing here? 我坐着想着我到底在做什么? But on the telephone line I am anyone 然而在电话里我可以是任何人 I am anything I want to be 任何事物 I could be a super model or Norman Mailer 我可以是超级模特或是诺曼第的邮递员 And you wouldnt know the difference 而你不会知道它的不同 Or would you? 或者你知道? In Santa Monica, all the people got modern names 在圣塔 莫尼卡,人们都有一个时髦的名字 Like Jake or Mandy 像杰克或曼蒂 And modern bodies too 还有现代的身躯 In Santa Monica, on the boulevard, 在圣塔 莫尼卡,在林荫大道上 Youll have to dodge those in-line skaters 你不得不躲开那些横冲直撞的溜冰者 Or theyll knock you down 否则他们会把你撞倒 I never felt so lonely, 我从未感到如此孤独 Never felt so out of place 从未感到如此与世界脱离 I never wanted something more than this 我从未这么渴望过一件事 But on the telephone line I am anyone 然而在电话里我可以是任何人 I am anything I want to be 任何事物 I could be a super model or Norman Mailer 我可以是超级模特或是诺曼第的邮递员 And you wouldnt know the difference 而你不会知道它的不同 On the telephone line, I am any height 在电话里我可以是我想要的任何高度, I am any age I want to be 任何年龄 I could be a caped crusader, or space invader 我可以是披着披肩的十字军,或是太空入侵者 And you wouldnt know the difference 而你不会知道它的不同 Or would you? 或者,你知道?

华为交换机中authentication-scheme default什么意思

authentication-scheme default是验证方式,default 是默认 默认情况下使用本地验证。 aaa aaa认证local-user huawei password simple huawei 设置用户及密码local-user huawei service-type telnet 设置此用户访问服务local-user huawei level 15 设置权限authentication-scheme default 验证方式默认及本地设备验证#authorization-scheme default 还是验证方式默认及本地设备验证#accounting-scheme default还是验证方式默认及本地设备验证#domain default 域 缺省。

They just want Ottawa to fork over additional bil

一、这个句子的语法结构如下: 〔主语〕They 〔谓语动词〕 want 〔宾语〕Ottawa 〔宾补〕to fork over additional billions with few strings attached 〔插入语〕 if any 〔程度状语〕just二、词语答疑 1、string 本义是 “一连串” 或 “一系列”,其复数 strings 由 “多系列” 转义为 “各种条件”,所以 strings attached 就是指 “附加的各种条件” 2、few 是半否定词,含义是 “几乎没有” 或 “为数不多”,此处修饰strings attached,意思是 “为数不多的附加条件”。三、译文:他们要求渥太华交付追加的数十亿而不带太多的附加条件。

粘贴cad时出现正在用 [bigfont.shx] 替换 [romand.shx]。指定插入点: ** 未定义的块 #-1是怎么回事

是字体替换,两个文件中使用的字体不同。你检查一下合并后的图形中字体都是什么。

在centos6中部署tomcat项目,但是总报java.net.ConnectException: Connection refused,请大神解惑

你项目中使用ftp下载文件,但是ftp服务拒绝了。ftp服务器的防火墙不让你链接ftp服务器如果是阿里云什么的,有安全组什么的。

当我运行JAVA时, 出现Exception in thread "AWT-EventQueue-0" java.util.ConcurrentModificationExceptio

1.首先看错误代码行:list 初始化了吗或者被赋值了吗,而且list 里的对象必须是string类型的。2.从异常看java.util.ConcurrentModificationException:字面意思并发修改异常。出现该异常一般是检测到对象的并发修改,但不允许这样修改,就会抛出这样的异常。3.当collection接口如list 被一个线程调用那么另一线程就不允许修改collection。

concurrentmodificationexception 是什么异常

看不到你源码不好说,ConcurrentModificationException这个错误是由于使用for(Object obj:objCollections){}这种语法时,在循环内部对objCollections这个集合对象做修改了而造成的

Java中使用addAll方法,抛出ConcurrentModificationException,请问问题出在哪儿?怎么解决?

subList方法返回的List和原来的List共享数据Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.

IBM ASMI 里的concurrent maintenance 菜单在哪

就在主菜单项里啊。

loadrunner 关于并发的问题 web_concurrent_start 和 lr_rendezvous

从概念上说 前者(web_concurrent_start)是语句的并发 后者(lr_rendezvous)是user的并发 这是两件完全完全不同的事情 没有什么可以比较的 仅仅只是都有“同时执行”的意思而已详细来说 URL-based 方式 默认是将每个请求录制成一条语句 而一条语句只建立一个到服务器的连接比方说 一个page上面 有图片 有文本 有音视频 有编辑框 有按钮 有链接 有复选框 等等等等……那么请求图片 请求文本 请求音视频…… 就上面所有那些 都各自分别是一条语句如果不写web_concurrent_start和web_concurrent_end函数 就默认按语句的顺序执行请求而写了web_concurrent_start和web_concurrent_end函数之后 就会将这些请求同时发送容易想象的是 并发请求时的压力 会比顺序请求的时候 要大 而集合点 或者也有叫同步点的 它的概念比较容易理解 就不解释了下面针对你的问题:“1用户下,使用web_concurrent_start(end)一次性提交20请求;和20用户下,通过rendezvous来集合后,每用户提交1个请求;这两种场景应该是一样的,因为都是一次向服务器同时提交了10个请求。”这是不准确的 原因至少有两点:第一 单用户多请求的并发性 要强于多用户的集合点这是因为 集合点是多线程的并发 它的并发性是有限的 宏观上是并发 微观上不可能并发因为如果你的电脑是单CPU的 那么你就不可能获得严格意义上的并发执行按照操作系统中 进程和线程的关系 在某一个时间点 严格上讲 就只有一个人得到执行除非你给每个用户配备一个CPU 才能达到真正的并发 但显然这是不可能的第二 你的每个请求的开销并不一定是相同的 这也导致测试结果的不可控最简单的 请求一段文字 与请求一段音视频 产生的系统开销肯定是不一样的你使用的web_custom_request函数 并不是发送完了就完了 而是返回完毕才算完成返回一段几KB的文字 与返回一段几MB的音视频 对网络的压力肯定是不一样的当然还可以有其他的理解 你可以自己继续分析而且可以预见的是 你这种测试 每一次都有可能获得不同的结果我指的是你请求的东西不一样的情况下 比如你换一个站点进行测试 结果就有可能是相反的原因就是我上面说的第二点

java.util.ConcurrentModificationException

看不到你源码不好说,ConcurrentModificationException这个错误是由于使用for(Object obj:objCollections){}这种语法时,在循环内部对objCollections这个集合对象做修改了而造成的

请问 java并发包中的 Thread exclusiveOwnerThread 为啥用 transient 修饰?

FixedThreadPool模式会使用一个优先固定数目的线程来处理若干数目的任务。规定数目的线程处理所有任务,一旦有线程处理完了任务就会被用来处理新的任务(如果有的话)。这种模式与上面的CachedThreadPool是不同的,CachedThreadPool模式下处理一定数量的任务的线程数目是不确定的。而FixedThreadPool模式下最多的线程数目是一定的。采用FixedThreadPool模式编写客户端程序如下:packagenet.jerryblog.concurrent;importjava.util.concurrent.ExecutorService;importjava.util.concurrent.Executors;publicclassFixedThreadPool{publicstaticvoidmain(String[]args){//三个线程来执行五个任务ExecutorServiceexec=Executors.newFixedThreadPool(3);for(inti=0;i<5;i++){exec.execute(newLiftOff());}exec.shutdown();}}3.SingleThreadExecutor模式SingleThreadExecutor模式只会创建一个线程。它和FixedThreadPool比较类似,不过线程数是一个。如果多个任务被提交给SingleThreadExecutor的话,那么这些任务会被保存在一个队列中,并且会按照任务提交的顺序,一个先执行完成再执行另外一个线程。SingleThreadExecutor模式可以保证只有一个任务会被执行。这种特点可以被用来处理共享资源的问题而不需要考虑同步的问题。SingleThreadExecutor模式编写的客户端程序如下:packagenet.jerryblog.concurrent;importjava.util.concurrent.ExecutorService;importjava.util.concurrent.Executors;publicclassSingleThreadExecutor{publicstaticvoidmain(String[]args){ExecutorServiceexec=Executors.newSingleThreadExecutor();for(inti=0;i<2;i++){exec.execute(newLiftOff());}}}这种模式下执行的结果如下:#0(9)#0(8)#0(7)#0(6)#0(5)#0(4)#0(3)#0(2)#0(1)#0(LiftOff!)第一个任务执行完了之后才开始执行第二个任务。

什么时候用到ConcurrentHashMap,什么时候不适合用?

多线程场景下使用。最直接的场景就是:热点缓存数据。(整个应用只有一份数据,所有线程都可以访问。同时,只能允许单个线程修改数据)非多线程访问同一资源场景下,不需要使用。

named user 和 concurrent user的区别

从概念上说 前者(web_concurrent_start)是语句的并发 后者(lr_rendezvous)是user的并发 这是两件完全完全不同的事情 没有什么可以比较的 仅仅只是都有“同时执行”的意思而已 详细来说

为什么java.util.concurrent 包里没有并发的ArrayList实现

ArrayList 是非线程安全的,这点已经在文档中指出来了。如果你想要一个线程安全的就用 CopyOnWriteArrayList。它在修改时把数据复制一份再来修改,因此后续修改不影响正在跑迭代的其它线程。如果你需要一个同步的就可以直接 List synchronizedList = Collections.synchronizedList(new ArrayList());每种实现类都有它的优势和缺点,按我们的需要选择一个合适的就可以了。

verilog 编译错误:Concurrent assignment to a non-net registerr is not permitted

调用子模块时 输出端口只能用wire类型变量进行映射 这是verilog语法规定的不知道你说的“无法实现想要的功能”是指什么 但是如果你需要输出信号是reg类型可以增加一个wire类型中间变量 再把这个中间变量赋值给一个reg类型变量wire a;testmodule tss(dataa,a,clockk);reg registerr;always @ * registerr <= a;

aix 如何判断vg是concurrent

比较vg的pvid,如果一样,说明这个vg是shared,算是concurrent

concurrent session是什么意思

并行会议

backport-util-concurrent是什么

backport-util-concurrent.jar并发访问处理端口的工具包。是LCDS的一部分

collections.synchronizedmap和concurrenthashmap的区别

最大的区别就是ConcurrentHashMap是线程安全的,hashMap不是线程安全的。为什么线程安全呢:ConcurrentHashMap代码中可以看出,它引入了一个“分段锁”的概念,具体可以理解为把一个大的Map拆分成N个小的HashTable,根据key.hashCode()来决定把key放到哪个HashTable中。在ConcurrentHashMap中,就是把Map分成了N个Segment,put和get的时候,都是现根据key.hashCode()算出放到哪个Segment中:

如何正确使用QtConcurrent运行类成员函数

使用QtConcurrent的代码如下:void MainDialog::on_pushButton_toGrayImage_QConcurrent_clicked(){QFuture<QImage*> future = QtConcurrent::run(this,&MainDialog::processImageByQtConcurrent);//imageAfterProceess 这个指针变量之前被无视,现在终于找到存在感了this->imageAfterProceess = future.result(); //接收处理结果this->showImageInNewWindow(this->imageAfterProceess);//新窗口显示处理后的图像}

ConcurrentHashMap内部排序的使用

业务中,我们经常会有队map进行排序的要求,如下将会详细讲解如何利用java8的lambda表达式实现map的内部排序。 首先,我们先构造一个person类: public class Person { private String addr; private String age; } 测试,对map进行排序处理。 import com.ky.common.Person; import java.util.*; import java.util.concurrent.ConcurrentHashMap; import java.util.stream.Collectors; import java.util.stream.Stream; import static java.util.Map.Entry.comparingByValue; import static java.util.stream.Collectors.toMap; public class Test { stream.sorted(Comparator.comparingInt(Map.Entry::getValue)).collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,(e1, e2)->e2, ConcurrentHashMap::new)); map.entrySet().stream().sorted(Comparator.comparing(Map.Entry::getValue)).forEach(System.out::println); }

java8 中concurrenthashmap数据结构和HashMap一样,且线程安全 为什么还要HashMap

java是编程语言里比较难学的一门,如果有心从事编程方向的工作,最好到专业机构学习并有更多的项目实践,更贴近市场,这样更有利于将来的发展。

concurrent.jar 包是做什么用的

jar包就是别人已经写好的一些类,然后将这些类进行打包,你可以将这些jar包引入你的项目中,然后就可以直接使用这些jar包中的类和属性了,这些jar包一般都会放在lib目录下的...呵呵

hashmap和concurrenthashmap哪个是线程安全的,为什么线程安全

ConcurrentHashMap是线程安全的,而HashMap不是线程安全的。在多线程环境下,如果多个线程同时读写同一个HashMap对象,可能会导致数据不一致的问题,例如两个线程同时往HashMap中添加数据,可能会导致数据丢失或覆盖。这是因为HashMap的实现不是线程安全的,它的内部结构是由数组和链表组成的,多个线程同时对它进行操作,会导致链表形成环形或链表断裂,导致数据读取或修改错误。ConcurrentHashMap是线程安全的原因是它采用了分段锁的机制,将HashMap分成若干个段(Segment),每个Segment独立地加锁,不同的线程可以同时访问不同的Segment,从而避免了多个线程同时访问同一个Segment的情况。这种机制可以提高并发访问效率,保证了线程安全性。

为什么java.concurrent.automic 里面没有string

因为String不是基础类型,而是对象,且是个Value Object(值对象)。你无法改变一个String对象的内容,你只能用另一个String的对象来替换原有的引用。例如:int i = 0;i++;//改变了原来的值String s = "xxx";//你无法改变原来的值s = "abc";//只能使用另外一个对象来替换因此atomic封装的String没有任何用处。atomic包是工具包,只是提供一个方便处理并发计数、改变标志的工具类,不能替代原来的基础类型和对象使用。

为什么CMS GC时出现Concurrent Mode Failure

出现Concurrent ModeFailure现象时,解决办法就是要让年老代留有足够的空间,以保证新对象空间的分配。另外在JVM BUG中有提到,JDK1.5_09版本之前,JVM参数-XX:CMSInitiatingOccupancyFraction是无效的,我这里应用环境的版本是JDK1.5_08,从gc日志来看是可以生效的。GC时还有一个常见的错误PromotionFailed,解决办法类似,也是调整年轻代和年老代的比例,还有CMSGC的时机。

ConCurrentHashMap 1.7 和 1.8 的区别

ConCurrentHashMap 1.8 相比 1.7的话,主要改变为: 下面简单介绍下主要的几个方法的一些区别: JDK1.7中的实现: ConCurrentHashMap 和 HashMap 的put()方法实现基本类似,所以主要讲一下为了实现并发性,ConCurrentHashMap 1.7 有了什么改变 JDK1.8中的实现: JDK1.7中的实现: JDK1.8中的实现: JDK1.7中的实现: JDK1.8中的实现: JDK1.7中的实现: JDK1.8中的实现: 由于没有segment的概念,所以只需要用一个 baseCount 变量来记录ConcurrentHashMap 当前 节点的个数 。

为什么java.util.concurrent 包里没有并发的ArrayList实现

你包引错了吧,让他自动引,如果还没有就是版本低了,要1.5还是1.6后面才有这个

Concurrent包中线程池问题:java中主函数执行完了为什么主线程还没有退出?是因为啥?都已经输出了横杠了.

那是因为你线程池没有关闭,所以主线程就不会退出,需要主线程退出只需要调用线程池的shutdown()方法,你的代码可以在main方法的最后一行加上 thr.shutdown(); 就可以了。

如何正确使用QtConcurrent运行类成员函数

使用QtConcurrent的代码如下:void MainDialog::on_pushButton_toGrayImage_QConcurrent_clicked(){ QFuture<QImage*> future = QtConcurrent::run(this,&MainDialog::processImageByQtConcurrent); //imageAfterProceess 这个指针变量之前被无视,现在终于找到存在感了 this->imageAfterProceess = future.result(); //接收处理结果 this->showImageInNewWindow(this->imageAfterProceess);//新窗口显示处理后的图像}

如何正确使用QtConcurrent运行类成员函数

使用QtConcurrent的代码如下:void MainDialog::on_pushButton_toGrayImage_QConcurrent_clicked(){ QFuture<QImage*> future = QtConcurrent::run(this,&MainDialog::processImageByQtConcurrent); //imageAfterProceess 这个指针变量之前被无视,现在终于找到存在感了 this->imageAfterProceess = future.result(); //接收处理结果 this->showImageInNewWindow(this->imageAfterProceess);//新窗口显示处理后的图像}

ConcurrentHashMap面试问题总结

Q:ConcurrentHashMap和HashMap的区别是什么? A: 1.ConcurrentHashMap是线程安全的,HashMap是线程不安全的 2.ConcurrentHashMap不允许Key为null的值插入。而HashMap是可以的 Q:JDK8的ConcurrentHashMap和JDK7的ConcurrentHashMap有什么区别? A: 1.JDK7的ConcurrentHashMap采用分段锁的策略,将整个数组分成多个segment,对这些segment进行分段加锁,使用的锁是ReentrantLock。而JDK8中的ConcurrentHashMap不采用分段锁的方式,直接使用Synchronized来进行。 2.JDK8中的ConcurrentHashMap新增了红黑树,并且插入用的是尾插法。 3.JDK7中的ConcurrentHashMap进行扩容时,是对当前的segment进行扩容,不会对其他segment有影响。而JDK8中就跟HashMap一样。整体扩容,但是保证线程安全 Q:JDK7中的ConcurrentHashMap是如何扩容的 A:JDK7中对每一段segment进行扩容,每一段segment的扩容跟HashMap保持一致 Q:JDK8中的ConcurrentHashMap是如何扩容的 A:在扩容时,首先会生成一个双倍大小的数组,生成完数组后,线程就会开始转移元素,在扩容的过程中,如果有其他线程在put,那么这个put线程会帮助去进行元素的转移,虽然叫转移,但是其实是基于原数组上的Node信息去生成一个新的Node的,也就是原数组上的Node不会消失,因为在扩容的过程中,如果有其他线程在get也是可以的。 Q:ConcurrentHashMap是如何保证线程安全的 A: 1.在JDK7的时候。ConcurrentHashMap是通过ReentrantLock+CAS+分段思想来保证的并发安全的,在JDK7的ConcurrentHashMap中,首先有一个Segment数组,存的是Segment对象,Segment相当于一个小HashMap,Segment内部有一个HashEntry的数组,也有扩容的阈值,同时Segment继承了ReentrantLock类,同时在Segment中还提供了put,get等方法,比如Segment的put方法在一开始就会去加锁,加到锁之后才会把key,value存到Segment中去,然后释放锁。同时在ConcurrentHashMap的put方法中,会通过CAS的方式把一个Segment对象存到Segment数组的某个位置中。同时因为一个Segment内部存在一个HashEntry数组,所以和HashMap对比来看,相当于分段了,每段里面是一个小的HashMap,每段公用一把锁,同时在ConcurrentHashMap的构造方法中是可以设置分段的数量的,叫做并发级别concurrencyLevel. 2.在JDK8的时候,ConcurrentHashMap是通过synchronized+cas来实现了。在JDK8中只有一个数组,就是Node数组,Node就是key,value,hashcode封装出来的对象,和HashMap中的Entry一样,在JDK8中通过对Node数组的某个index位置的元素进行同步,达到该index位置的并发安全。同时内部也利用了CAS对数组的某个位置进行并发安全的赋值。

concurrent.futures 模块怎么安装 或者concurrent 模块也可以

如果是python2.x,直接在命令提示符中用pip install futures语句安装,concurrent就可以用了。如果是python3,不用安装也可以用,自带了。参看:https://stackoverflow.com/questions/31086530/importerror-no-module-named-concurrent-futures-process

ConcurrentHashMap常问问题

采用了分段锁的思想,将哈希桶数组分成一个个的Segment数组(继承ReentrantLock),每一个Segment里面又有多个HashEntry,也是被volatile修饰的,是为了保证在数组扩容时候的可见性,HashEntry中又有key,hash,value,next属性,而value,next又是被volatile修饰为了保证多线程环境下数据修改时的可见性,多线程环境下ConcurrentHashMap会对这些小的数组进行加锁,这样多线程操作Map就相当于是操作单线程环境下的HashMap,比如A线程对其中一个段进行写操作的时候线程B就不能对其进行写操作,但是线程B可以对其他的段进行写操作,从而实现并发修改和访问。 JDK1.8的ConcurrentHashMap摒弃了分段锁的思想,采用jdk1.8中HashMap的底层机构,Node数组+链表+红黑树。Node是继承了Entry的一个内部类,他的value和next都是被volatile修饰的原因也是为了保证多线程下修改数据的可见性。 采用CAS+synchronized实现更加细粒度的锁,将锁的级别控制在更细粒度的哈希桶数组元素的级别,只需要锁住链表头节点(红黑树的根节点)就不会影响到其他哈希桶数组元素的读写,大大的提高了并发度。 是不需要加锁的,因为Node节点使用了volatile修饰了value和next节点,而在jdk8中同样也是使用了volatile修饰了value和next节点,这样保证可见性了就不需要加锁了。 key不能为空,无法解释,没有什么可说的,可能就是作者的想法。 value不能为空是因为ConcurrentHashMap是工作在多线程环境下的,如果调用get方法,返回null,这个时候就存在二义性,因为ConcurrentHashMap不知道是没有这个key,还是这个key对应的值是不是null。所以干脆不支持value为null。 HashMap的迭代器是强一致性的,而ConcurrentHashMap的迭代器是弱一致性的,因为在多线程环境下,在创建迭代器的过程中,内部的元素会发生变化,如果是在已经遍历过去的数据中发生变化,迭代器是无法反映出来数据发生了改变,如果是发生在未迭代的数据时,这个时候就会反映出来,强一致性就是说只要迭代器创建出来之后数据就不会发生改变了。这样设计的好处就是迭代器线程可以使用原来的老数据进行遍历,写线程可以并发的完成改变,这样就保证了多个线程执行的时候的连续性和可拓展性,提升了并发性能。 JDK1.7中,并发度就是ConcurrentHashMap中的分段个数,即Segment[]数组的长度,默认是16,这个值可以在构造函数中设置。如果自己设置了并发度那么就会和HasHMap一样会去找到大于等于当前输入值的最小的2的幂指数作为实际并发度。如果过小就会产生锁竞争,如果过大,那么就会导致本来位于同一个Segment的的访问会扩散到不同的Segment中,导致性能下降。 JDK1.8中摈弃了Segment的概念,选择使用HashMap的结构,并发度依赖于数组的大小。 ConcurrentHashMap效率高,因为hashTable是给整个hash表加锁,而ConcurrentHashMap锁粒度要更低。 使用Collections.synchronizedMap(Map类型的对象)方法进行同步加锁,把对象转换为SynchronizedMap<K,V>类型。其实就是对HashMap做了一次封装,多个线程竞争一个mutex对象锁,在竞争激烈的情况下性能也非常差,不推荐使用。

concurrent with是什么意思

同时 一致

jdk8中的ConcurrentHashMap究竟为什么高效?

从源码来窥其一斑! 我们都知道hashMap不是线程安全的,因为在扩容方法中很容易出现死循环,hashTable使用锁的方式比较简单暴力,几乎在所有操作方法上都加了synchronized锁,导致总体性能很差,concurrentHashmap凭借线程安全且性能优异一直都是高并发中的首选key-value型数据结构; concurrentHashmap的高性能有以下原因: 一,分段锁:jdk8中对concurrentHashmap进行了改进,抛弃了jdk7中新建segment作为分段锁的过程,jdk8中虽沿用了这种分段锁的思想,却直接使用数组中的数据作为 分段锁保证concurrentHashmap在上锁的时候只针对数组下标下的数据进行上锁 (比如如果数组长度为256,那么每次put平均只有1/256的数据被锁),而大多数其他的数据还是能进行正常的增删改操作,无需阻塞等待,这无疑极大的 降低了锁的粒度,提升了性能。 二,红黑树 :jdk8中引入了红黑树结构,在单个数组下标内的数据达到8以后,会自动转换为红黑树进行存储, 使用大O表示法表示效率的话,红黑树的查找效率为O(log(n)),而链表的效率为O(n) ,当数据量越来越大的时候,红黑树的效率明显好于链表,所以concurrentHashmap性能得到很大提升; 现在我们主要从put方法中的主要方法来分析性能的提升: spread(key.hashCode());//作用是再次哈希,减少冲突 ,源码如下其中涉及到的位运算有 >>> 16:无符号右移16位,空位以0补齐 。 ^:异或运算符-->相同为0,不同为1; &:与运算符-->全1得1,否则0; (h ^ (h >>> 16)) & HASH_BITS; 所以这句代码的意思就是不仅消除高16位的影响,同时获得正整数的hash值 再来看后面的方法, 如上图: 1,就是判断当这个hash表还是空的时候,调用initTable进行初始化; 2,使用(n - 1) & hash)计算数组下标,如果数据指定下标处为null,则直接插入,注: cas是java8中的concurrentHashmap引入的线程安全判断,CAS算法做为乐观锁 ; 3,(fh = f.hash) == MOVED,走到此处说明下标内有node,且该node的值为-1(MODED=-1),搜索全类发现MODED是在调用有参构造器ForwardingNode中默认写入的,而这个调用处刚好在transfer方法中,所以我们推断,扩容的时候先将数组下标内的node.hash置为-1! 同时在3这一步中调用helpTransfer(tab, f)参与扩容,并把数据写入;4,走到这说明node不是空的,也没在扩容,那么锁住该下标下的node,并把新value插入链表中; 5,如果锁住的这个node能实例化为TreeBin,则代表已经转化为红黑树进行存储,将数据插入红黑树中; 6,判断在4,5中计算得到的数组下标内所有节点总数, 如果满足转化为红黑树的条件(节点数大于8),则自动转化为红黑树进行存储! 总的来说,concurrentHashmap之所以性能高就是因为使用了分段锁和红黑树! 至于conrrentHashmap其他的方法的源码分析,后期会补上的,更多的技术分享,敬请关注!

concurrentmap为什么线程安全

concurrentmap线程安全原因:1、JDK1.7中,ConcurrentHashMap使用的锁分段技术,将数据分成一段一段的存储,然后给每一段数据配一把锁,当一个线程占用锁访问其中一个段数据的时候,其他段的数据也能被其他线程访问。2、JDK1.8放弃了锁分段的做法,采用CAS和synchronized方式处理并发。以put操作为例,CAS方式确定key的数组下标,synchronized保证链表节点的同步效果。
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