I met with a few companies and talked to the interviewer about his previous work and areas of expertise. After understanding, the interviewer looked at his resume and asked: "Have you done a high-concurrency project? Can your system support high-concurrency? In high-concurrency scenarios, which distribution methods in load balancing will you use? How do you think the million-traffic technology should be selected?" After hearing this question, I was taken aback. Why did this company also ask high-concurrency? ? I thought about some high-concurrency articles and materials that I had read before, and said it all over again. I haven't been exposed to high concurrency before, and the answer is illogical, and I don't know where to start. When I will answer the next interview questions, I am not as confident as I was at the beginning, and I will know that I am out of the picture by looking at the attitude of the interviewer.
Need high concurrency everywhere
** "Why do Java interviews have to ask about high concurrency?" ** This question has caused programmers to feel headaches, especially programmers who want to move to a larger company. Whether they can answer high concurrency questions beautifully has become a job search. Whether the person is a good programmer is judged by a big factory interview. It has to be said that the highest concurrency test is the programmer's strength and practical experience. **As the traffic increases, high concurrency has become an inevitable topic. When dealing with high concurrency, more and more technical problems will be encountered, such as interface response timeout, increased CPU load, deadlock, A series of problems such as frequent GC and large data storage. It can be said that if you can't deal with high concurrency, you can only gradually be eliminated in the end. Therefore, it is not surprising that high concurrency often appears in the interview questions of big companies. Speaking of this, you may have questions: you know that your company's business does not involve high concurrency, and there are not many users. There is no need for high-concurrency architecture design. How can you get in touch with high-concurrency projects?
How to truly master high concurrency
If you want to continue to advance, you can't rely on the company's business to exercise yourself. In our spare time, we can also learn on our own. Many bosses also improve themselves because of their needs. The increase in demand and the development of technology promote our continuous improvement in the depth of technology. Only after upgrading one's own technology, will the scope of employment options be wider, and the span of income growth will also be greater.
However, in the process of diligence, many people have a taste of high concurrency and cannot learn deeply.
I do
n’t know which indicators should be used to measure the high concurrency system; I don’t know which technical solution should be used to solve the high concurrency problem in different scenarios; it is
impossible to implement the solution to achieve performance pressure measurement;
…
It can be seen that in order to fully master a new skill, one cannot just learn theoretical knowledge. In terms of operation, the experience accumulated in practice often has a greater impact on the improvement of technology. **However, because there is no opportunity to access high-concurrency business scenarios, and no relevant experience can be found on the search website, we have formed a technical barrier on the road to contact high-concurrency, making it difficult for us to move forward.
Then I will also share with you my specific learning route and notes in the past 6 years, hoping to help friends who are interested in improving technology. This learning route not only talks about high concurrency, but also organizes Android development trends from many aspects. Good several technical outlines and materials
360° all-round performance tuning
Performance optimization is for the entire app development. When a good project is developed, not only is the product better, the developer also needs to know why the app I developed can run on most mobile phones, and why most mobile phones do not have bugs when users use it. Our apk file can be optimized to be very small. For example, if you make a project, it may be 10m after packaging, but after optimization, it may only be 8m or even smaller. In addition, how safe is the project we are doing? Why do we conclude that the app we made is safe? These are all involved in performance optimization.
1. Design ideas and code quality optimization
Whether an app’s performance is good or not, we need to work on two levels. The first level: you need to pay attention when writing code, make your own code high-performance and high-availability code, this process is to write high-performance code; the second level: check the code problem with tools for the already formed code , To guide us to delete and modify the code through the checked problems, this process is called tuning.
How to write high-performance code? Then we need to have a deep code knowledge, which is the basis of the code, such as: the data structure can be written according to the application scenario to meet the current scenario of the special structure, for example, Google developed sparseArray instead of HashMap for the characteristics of the Android platform. In addition, he has his own unique insights into commonly used algorithms. There are hundreds of questions on LeetCode, so that you can almost achieve the ability to be proficient in the most commonly used algorithms such as sorting and searching dynamic programming. Furthermore, if efficient algorithms and memory-saving data structures are matched with excellent design patterns that meet application scenarios, these provide a basis for high-performance code.
The other is to tune the written code. Then the direction of tuning is to use the Profiler tool to test and check to see where there are performance-consuming operations, and then analyze the problems with the code. The direction of tuning becomes how to optimize memory, power consumption, network traffic, and of course, there are reasons for startup speed, page switching effect and speed, boot white screen experience, and splash screen. Wait for analysis and tuning. Finally, add a screen adapter camera adapter.
2. Program performance optimization
Start-up speed and execution efficiency optimization
layout detection and optimization
memory optimization
power consumption optimization
network transmission and data storage optimization
APK size optimization
3. Optimization of development efficiency
Distributed version control system Git
automated build system Gradle
4. Project actual combat
Start-up speed, fluency, practice of Douyin in APK package size resource optimization, Youku responsive layout technology, full analysis, network optimization, mobile phone Taobao double eleven performance optimization project, revealing the source code dependence analysis of the entire link of AutoNavi APP, and completely eliminating OOM actual combat experience sharing WeChat Android Terminal memory optimization practice
Benchmarking the necessary technologies for Tencent T3.3 architects
Android framework architecture (advanced UI+FrameWork source code) This piece of knowledge is currently the most users, and we call it the technology of Android from 2013 to 2016.
Android developers are often familiar and unfamiliar with this frequently "used" code because they are used to copying code online: the familiar is dealing with them almost every day, and copying the code every day; the unfamiliar is that although with these codes every day Dealing with codes, but I haven't studied the principles of these codes in depth and the connotations in the depths of the codes.
Key points of knowledge in this article:
1. Code design guidelines necessary for architects
2. Component-based architecture design
3. Plug-in architecture design
4. Hot fix design
5. Open source framework source code analysis and implementation
At present, the mainstream language for Android APP development is the Java language. The biggest feature of the Java language is to increase the possibility of software interaction. It can be said that almost all applications on Android phones are written in the Java language.
Knowledge points:
1. Java serialization, generics, reflection
2. The underlying principle of virtual machine
3. Android memory principle
4. Java high concurrency principle detailed explanation
5. Compile-time technology mastery and actual combat
6. JDK advanced dynamic agent
7. Advanced data structure And algorithm
8, Java IO operation
Android R Frame Work source code and UI
In Android, Framework refers to the system architecture layer. Framework means "framework" in Chinese. In software development, it usually refers to the development framework. It is above the kernel layer in a system and provides interfaces for top-level applications. It is designed to help developers quickly develop top-level applications without having to care about the system. The kernel operating mechanism, usually Framework will hide the main function and other necessary components of the application, developers only need to focus on the realization of the function code. To put it simply, the specific work of Framework is to provide a series of services and API interfaces for developers of android application development.
UI does not simply refer to the effect the user sees. Because in Android development, there is a deep-level system behind each control. Naturally, UI does not simply refer to custom controls. We should also know the execution process behind custom controls, including from Activity Creation, analysis of XML, measurement, layout, and drawing of each control. Of course, there are also knowledge points such as animation, event distribution mechanism, and nested sliding mechanism. There are also some UI frameworks provided by Google that also enable us to grasp the objects, such as Jetpack component library, Material Design, etc.
Knowledge points:
1. FrameWork source code analysis
2. In-depth analysis of common Android components
3. In-depth analysis and customization of UI
4. Jetpack family bucket
5. Android R
6, RXJava responsive programming framework design
Advanced audio and video (audio and video series)
From the perspective of future trends, with the advent of the 5G era, audio and video have gradually become necessities in people's daily lives. In addition to online education, audio and video conferences, and instant messaging products that must use audio and video technology, other products also need to add audio and video elements.
It is precisely because of such a big trend that in addition to major factories, other small factories are also starting to look for audio and video talents.
A slightly better audio and video talent may now have 3-4 companies rushing to get it, earning it. The demand for audio and video talents has changed from a niche to the general public, which is more a result of everyone's expectations of the future market.
Why are audio and video talents rare?
Audio and video knowledge is complex, and there are very few easy-to-understand materials;
Online blogs and videos are filled with a lot of wrong information, making many beginners unable to climb out of the pit.
For example, according to the traditional audio and video learning method: first contact a large number of audio and video open source libraries, such as FFmpeg, MediaCodec, and often these APIs have already made your head bigger. Staying on the API will not allow you to adapt to changing needs. The first direction was wrong. No matter how hard I tried, I couldn't learn audio and video.
Key points of this article:
1. Basic syntax
2. H264 video coding
3. H265 coding principle
4. H265 coding application
5. MediaCode
- Interpretation of Android-related source code
As long as it is a programmer, whether it is Java or Android, if you don’t read the source code and only look at the API documentation, it will just stay on the skin. This is not good for the establishment and completeness of our knowledge system and the improvement of actual combat technology. of.
In order to make learning easy and efficient! Today, I helped you organize the above knowledge points to be learned in **[ Github ] , friends who need to read all the core knowledge points can go to my [ Github ]** to check; hope to help you learn and advance In the middle, light up a lamp that illuminates the mist;
Those who need high-definition PDF version can click here and click here (get it directly)
