清风渡

问题集锦

2019-11-28T03:50:00+00:00

设计原理

uuid 是否有重复？
- 自动 id 生成策略
- 分布式 id 生成原理
线程池
前 10 个 ip，内存不足

项目

Storm/Flink 消息有序性保证
蓄洪机制原理
storm-jms 模块修改
ugc 视频生产优化
工作流引擎原理
MySQL 分库分表原因
推荐机制
Neo4j 原理，社区版和商业版，对比其他图数据库

Spring

Hibernate 优缺点，Mybatis 优缺点，为什么都用 Mybatis？
Spring 启动过程？
Bean 加载过程
AOP 原理（字节码层面）
循环依赖
Spring Boot 自动注入配置原理过程
事务传播级别
Spring Interceptor 机制，以及和 filter 区别关系？

RPC 框架

设计一个 RPC 框架
RPC 框架通讯协议
常见 RPC 框架，优缺点，原理

网络

三次握手，四次挥手，包括状态变化
拥塞
滑动窗口
MTU/MSS
可靠性如何保证
HTTP(S)协议，HTTP1/2

Java

HashMap 原理
多线程编程，CountLatch、CyclicBarrier
Volatile/Synchronized
可重入锁、自旋锁、偏向锁、轻量级锁
多线程环境下单例的两种实现（effective java)，以及 volatile 存在的意义
线程池原理
实现简单的线程池
多路复用 IO 为何比非阻塞 IO 的效率更高？
- 非阻塞 IO 中，不断地询问 socket 状态是通过用户线程进行的，在多路复用 IO 中，轮训每个 socket 状态是内核中进行的，效率要比用户线程要高
Java IO/NIO
- 阻塞 IO
- 非阻塞 IO
- 多路复用 IO
- 信号驱动 IO
- 异步 IO
  - 只需先发送一个请求，当接收内核返回的成功信号时表示 IO 操作已经完成，可以直接去使用数据
Java NIO

三大核心：Channel, Buffer, Selector
IO 是面向流的，NIO 是面向缓冲区的

HashMap

bucket
两倍扩容
负载因子为 0.75
数组+链表+红黑树（阈值是 8）

ConcurrentHashMap

Java7：Segment，并行级别默认是 16
Java8：CAS, 红黑树

JVM

运行时数据区划分
垃圾回收
类加载过程

加载、验证、准备、解析、初始化、使用、卸载

栈帧
- 一个线程中，每调用一个方法创建一个栈帧
- 栈帧结构
  - 本地变量表
  - 操作数栈
  - 动态链接
  - 方法出口
内存溢出和内存泄漏的区别
StackOverFlow 和 OutOfMemory 区别
对象从新生代移到老年代的条件
Java8 中永久代被移出，由元空间取代，使用本地内存，字符串池和类的静态变量放入 java 堆中
GC Roots 有哪些？
- VM 栈中的引用
- 方法区中的静态变量
- JNI 中的引用
垃圾收集算法
- 标记清除
  - 内存碎片化严重
- 复制
  - 可用内存被压缩到一半，如果存活对象增多，效率会低
- 标记整理
- 分代收集
垃圾收集器
- Serial
  - 新生代，复制算法，单个 CPU 环境
- ParNew
  - 新生代，复制算法，Serial 的多线程版本
- Parallel Scavenge
  - 新生代，复制算法，多线程
  - 可控制的吞吐量，CPU 运行用户代码的时间/CPU 总消耗时间
  - 自适应调节策略
- Serial Old
  - Serial 的老年代版本，单线程，标记整理算法
  - CMS 的后备方案
- Parallel Old
  - Parallel Scavenge 的年老代版本，多线程，标记整理算法
- CMS
  - 多线程，标记清除算法
  - 初始标记、并发标记、重新标记、并发清除
- G1
  - 标记整理，无内存碎片，低停顿
  - 区域划分、优先级区域回收
类加载器

启动类加载器、扩展类加载器、应用程序类加载器

双亲委派模型

当一个类加载器收到了类加载请求，会把这个请求委派给父类加载器，只有父类加载器反馈自己无法完成时，子类加载器才会尝试自己去加载。好处是保证了使用不同类加载器最终得到的都是同样一个对象。
双亲其实就是父亲

排序算法

快排

算法

图

路径查找

树

红黑树

Effective Java

分布式

分布式事务
分布式锁

数据库

聚簇索引和非聚簇索引
主键索引和联合索引

试一试Jekyll

2019-10-08T05:49:30+00:00

第一次用Jekyll，尝尝鲜！

还不错

Welcome to Jekyll!

2019-04-18T19:34:30+00:00

You’ll find this post in your _posts directory. Go ahead and edit it and re-build the site to see your changes. You can rebuild the site in many different ways, but the most common way is to run jekyll serve, which launches a web server and auto-regenerates your site when a file is updated.

To add new posts, simply add a file in the _posts directory that follows the convention YYYY-MM-DD-name-of-post.ext and includes the necessary front matter. Take a look at the source for this post to get an idea about how it works.

Jekyll also offers powerful support for code snippets:

def print_hi(name)
  puts "Hi, #{name}"
end
print_hi('Tom')
#=> prints 'Hi, Tom' to STDOUT.

Check out the Jekyll docs for more info on how to get the most out of Jekyll. File all bugs/feature requests at Jekyll’s GitHub repo. If you have questions, you can ask them on Jekyll Talk.

Post: Link

2010-03-07T00:00:00+00:00

This theme supports link posts, made famous by John Gruber. To use, just add link: http://url-you-want-linked to the post’s YAML front matter and you’re done.

And this is how a quote looks.

Some link can also be shown.

Post: Notice

2010-02-05T00:00:00+00:00

A notice displays information that explains nearby content. Often used to call attention to a particular detail.

When using Kramdown {: .notice} can be added after a sentence to assign the .notice to the <p></p> element.

Changes in Service: We just updated our privacy policy here to better service our customers. We recommend reviewing the changes.

Primary Notice: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer nec odio. Praesent libero. Sed cursus ante dapibus diam. Sed nisi. Nulla quis sem at nibh elementum imperdiet.

Info Notice: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer nec odio. Praesent libero. Sed cursus ante dapibus diam. Sed nisi. Nulla quis sem at nibh elementum imperdiet.

Warning Notice: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer nec odio. Praesent libero. Sed cursus ante dapibus diam. Sed nisi. Nulla quis sem at nibh elementum imperdiet.

Danger Notice: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer nec odio. Praesent libero. Sed cursus ante dapibus diam. Sed nisi. Nulla quis sem at nibh elementum imperdiet.

Success Notice: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer nec odio. Praesent libero. Sed cursus ante dapibus diam. Sed nisi. Nulla quis sem at nibh elementum imperdiet.

Want to wrap several paragraphs or other elements in a notice? Using Liquid to capture the content and then filter it with markdownify is a good way to go.

{% capture notice-2 %}
#### New Site Features

* You can now have cover images on blog pages
* Drafts will now auto-save while writing
{% endcapture %}

<div class="notice">{{ notice-2 | markdownify }}</div>

New Site Features

You can now have cover images on blog pages
Drafts will now auto-save while writing

Or you could skip the capture and stick with straight HTML.

<div class="notice">
  <h4>Message</h4>
  <p>A basic message.</p>
</div>

Message

A basic message.

Post: Quote

2010-02-05T00:00:00+00:00

Only one thing is impossible for God: To find any sense in any copyright law on the planet.

Mark Twain

Post: Chat

2010-01-08T00:00:00+00:00

Abbott: Strange as it may seem, they give ball players nowadays very peculiar names.

Costello: Funny names?

Abbott: Nicknames, nicknames. Now, on the St. Louis team we have Who’s on first, What’s on second, I Don’t Know is on third–

Costello: That’s what I want to find out. I want you to tell me the names of the fellows on the St. Louis team.

Abbott: I’m telling you. Who’s on first, What’s on second, I Don’t Know is on third–

Costello: You know the fellows’ names?

Abbott: Yes.

Costello: Well, then who’s playing first?

Abbott: Yes.

Costello: I mean the fellow’s name on first base.

Abbott: Who.

Costello: The fellow playin’ first base.

Abbott: Who.

Costello: The guy on first base.

Abbott: Who is on first.

Costello: Well, what are you askin’ me for?

Abbott: I’m not asking you–I’m telling you. Who is on first.

Costello: I’m asking you–who’s on first?

Abbott: That’s the man’s name.

Costello: That’s who’s name?

Abbott: Yes.

Costello: When you pay off the first baseman every month, who gets the money?

Abbott: Every dollar of it. And why not, the man’s entitled to it.

Costello: Who is?

Abbott: Yes.

Costello: So who gets it?

Abbott: Why shouldn’t he? Sometimes his wife comes down and collects it.

Costello: Who’s wife?

Abbott: Yes. After all, the man earns it.

Costello: Who does?

Abbott: Absolutely.

Costello: Well, all I’m trying to find out is what’s the guy’s name on first base?

Abbott: Oh, no, no. What is on second base.

Costello: I’m not asking you who’s on second.

Abbott: Who’s on first!

Costello: St. Louis has a good outfield?

Abbott: Oh, absolutely.

Costello: The left fielder’s name?

Abbott: Why.

Costello: I don’t know, I just thought I’d ask.

Abbott: Well, I just thought I’d tell you.

Costello: Then tell me who’s playing left field?

Abbott: Who’s playing first.

Costello: Stay out of the infield! The left fielder’s name?

Abbott: Why.

Costello: Because.

Abbott: Oh, he’s center field.

Costello: Wait a minute. You got a pitcher on this team?

Abbott: Wouldn’t this be a fine team without a pitcher?

Costello: Tell me the pitcher’s name.

Abbott: Tomorrow.

Costello: Now, when the guy at bat bunts the ball–me being a good catcher–I want to throw the guy out at first base, so I pick up the ball and throw it to who?

Abbott: Now, that’s he first thing you’ve said right.

Costello: I DON’T EVEN KNOW WHAT I’M TALKING ABOUT!

Abbott: Don’t get excited. Take it easy.

Costello: I throw the ball to first base, whoever it is grabs the ball, so the guy runs to second. Who picks up the ball and throws it to what. What throws it to I don’t know. I don’t know throws it back to tomorrow–a triple play.

Abbott: Yeah, it could be.

Costello: Another guy gets up and it’s a long ball to center.

Abbott: Because.

Costello: Why? I don’t know. And I don’t care.

Abbott: What was that?

Costello: I said, I DON’T CARE!

Abbott: Oh, that’s our shortstop!

Post: Modified Date

2010-01-07T00:00:00+00:00

This post has been updated and should show a modified date if used in a layout.

All children, except one, grow up. They soon know that they will grow up, and the way Wendy knew was this. One day when she was two years old she was playing in a garden, and she plucked another flower and ran with it to her mother. I suppose she must have looked rather delightful, for Mrs. Darling put her hand to her heart and cried, “Oh, why can’t you remain like this for ever!” This was all that passed between them on the subject, but henceforth Wendy knew that she must grow up. You always know after you are two. Two is the beginning of the end.

Post: Standard

2010-01-07T00:00:00+00:00

Mrs. Darling first heard of Peter when she was tidying up her children’s minds. It is the nightly custom of every good mother after her children are asleep to rummage in their minds and put things straight for next morning, repacking into their proper places the many articles that have wandered during the day.

This post has a manual excerpt  set after the second paragraph. The following YAML Front Matter has also be applied:

excerpt_separator: "<!--more-->"

If you could keep awake (but of course you can’t) you would see your own mother doing this, and you would find it very interesting to watch her. It is quite like tidying up drawers. You would see her on her knees, I expect, lingering humorously over some of your contents, wondering where on earth you had picked this thing up, making discoveries sweet and not so sweet, pressing this to her cheek as if it were as nice as a kitten, and hurriedly stowing that out of sight. When you wake in the morning, the naughtiness and evil passions with which you went to bed have been folded up small and placed at the bottom of your mind and on the top, beautifully aired, are spread out your prettier thoughts, ready for you to put on.

I don’t know whether you have ever seen a map of a person’s mind. Doctors sometimes draw maps of other parts of you, and your own map can become intensely interesting, but catch them trying to draw a map of a child’s mind, which is not only confused, but keeps going round all the time. There are zigzag lines on it, just like your temperature on a card, and these are probably roads in the island, for the Neverland is always more or less an island, with astonishing splashes of colour here and there, and coral reefs and rakish-looking craft in the offing, and savages and lonely lairs, and gnomes who are mostly tailors, and caves through which a river runs, and princes with six elder brothers, and a hut fast going to decay, and one very small old lady with a hooked nose. It would be an easy map if that were all, but there is also first day at school, religion, fathers, the round pond, needle-work, murders, hangings, verbs that take the dative, chocolate pudding day, getting into braces, say ninety-nine, three-pence for pulling out your tooth yourself, and so on, and either these are part of the island or they are another map showing through, and it is all rather confusing, especially as nothing will stand still.

Of course the Neverlands vary a good deal. John’s, for instance, had a lagoon with flamingoes flying over it at which John was shooting, while Michael, who was very small, had a flamingo with lagoons flying over it. John lived in a boat turned upside down on the sands, Michael in a wigwam, Wendy in a house of leaves deftly sewn together. John had no friends, Michael had friends at night, Wendy had a pet wolf forsaken by its parents, but on the whole the Neverlands have a family resemblance, and if they stood still in a row you could say of them that they have each other’s nose, and so forth. On these magic shores children at play are for ever beaching their coracles [simple boat]. We too have been there; we can still hear the sound of the surf, though we shall land no more.

Of all delectable islands the Neverland is the snuggest and most compact, not large and sprawly, you know, with tedious distances between one adventure and another, but nicely crammed. When you play at it by day with the chairs and table-cloth, it is not in the least alarming, but in the two minutes before you go to sleep it becomes very real. That is why there are night-lights.

Occasionally in her travels through her children’s minds Mrs. Darling found things she could not understand, and of these quite the most perplexing was the word Peter. She knew of no Peter, and yet he was here and there in John and Michael’s minds, while Wendy’s began to be scrawled all over with him. The name stood out in bolder letters than any of the other words, and as Mrs. Darling gazed she felt that it had an oddly cocky appearance.