Preface
A three-piece interview for Java programmers in 2020: multithreading + algorithm + microservices. For those who want to interview for advanced Java positions, algorithm + multithreading + microservice is a barrier that can't be bypassed! The remaining topics for the actual work belong to the real skill, and the details and difficulties of popular technologies become the main content of the interview.
The editor here recommends the following three learning manuals for the three knowledge points of multi-threading + algorithm + microservices . These three books are selected by the editor at the cost of baldness and carefully researched and selected, so that everyone has an understanding of these three knowledge frameworks A basic outline, there is no problem dealing with an interview;
Multithreading
Speaking of multi-threaded programming, I am afraid that many developers will shake their heads to indicate that they don't understand. Indeed, students and newly employed developers often rarely have the opportunity to practice multi-threaded programming. In most cases, they write single-threaded business code under the development framework, and the multi-threaded part is encapsulated inside the framework. Even experienced developers will lament that they have had some trouble with multithreading. But it is undeniable that multi-threading is indeed a weapon, and the use of multi-threading helps to improve the responsiveness and throughput of the program. It is no exaggeration to say that multithreading is a "monster" that developers must defeat in the process of continuing to "upgrade".
The term " design pattern " often makes developers feel intimidated. In fact, design patterns are just a summary and induction of code design methods. In our code, design patterns are everywhere, but we didn't notice them. Making good use of design patterns can help us write code that is highly reusable and loosely coupled.
So, if you put the two themes of "multithreading" and "design patterns" together today, have you already begun to look forward to and fearful? But software development is such an interesting thing-as the fear in our hearts grows day by day, the mood to try to challenge will become more and more urgent.
Recommended reason:
I wrote 300 Java sample programs to implement design patterns. Mastering these design patterns can avoid program deadlock, save resources, improve performance, etc., and make multithreaded programs more efficient. The java.util.concurrent package, synchronized keyword, Swing framework, Java memory model, etc. are also involved. Not only can we understand the relevant knowledge of Java multithreading, but also can deepen the understanding of the Java language;
Friends who need this "Multithreading and Design Patterns" manual can get it for free by adding the end of the article after just like + follow;
brief introduction:
Chapter 1 : " Single Threaded Execution Mode-Only one person can cross the bridge " will introduce the most basic design pattern in multithreaded programming-Single Threaded Execution mode. This mode can ensure that there can only be one thread performing processing, which can effectively prevent instance inconsistency. This chapter will also introduce the synchronized keyword of the Java language in depth, and give a sample program for counting the semaphore java.util.concurrent.Semaphore.
Chapter 2 : " Immutable Mode-If you want to destroy it, you can't destroy it " will introduce the Immutable mode, which is a mode in which the content cannot be changed once an instance is created. In this mode, since the instances will not be inconsistent, there is no need to perform mutual exclusion processing, and program performance can also be improved. This chapter will also describe the meaning of final in the Java language, and give sample programs for collections.synchronizedList and java.util.concurrent.copyonwriteArrayList.
Chapter 3 : " Guarded Suspension Mode-Wait for me to get ready " will introduce the Guarded Suspension mode, which prevents the thread from continuing to execute before the instance enters the target state. This mode can also prevent instance inconsistency. Through this chapter, you can also practice the use of the wait method and notifyAll method in the Java language. This chapter will also give a sample program for blocking queue java.util.concurrent.LinkedBlockingQueue.
Chapter 4 : " Balking Mode-Don't Need It " will introduce the Balking mode, which is a mode in which method execution is interrupted if the instance does not enter the target state. This mode prevents the execution of invalid waits and redundant methods.
Chapter 5 : " Producer-Consumer Mode-I will do it, you will use it " will introduce the Producer-Consumer mode. In this mode, multiple threads can run in coordination. When this mode is adopted, the thread that generates the data and the thread that uses the data will not preempt each other when running concurrently. This chapter will also give a sample program of blocking queue java.util.concurrent.ArrayBlockingQueue.
Chapter 6: " Read-Write Lock mode-everyone can read together, but don't write when reading " will introduce the Read-Write Lock mode, which uses flexible mutual exclusion processing. In this mode, there can only be one thread that writes data, but there can be many threads that read data. This mode can improve the overall performance of the program. This chapter will also give a sample program of reentrant java.util.concurrent.locks.ReentrantReadWriteLock.
Chapter 7 "Thread-Per-Message Mode-This work is up to you" will introduce the Thread-Per-Message mode, a mode that delegates processing to other threads. In this mode, the thread can delegate tasks to other threads, and directly handle the next work. This mode can improve the responsiveness of the program. This chapter will also introduce the use of internal classes in the Java language, and give sample programs of Executor and Executorservice in the java.util.concurrent package.
Chapter 8 "Worker Thread Mode—Wait until Work Comes, Work When Work Comes" will introduce the WorkerThread mode, which is a mode in which multiple threads wait through the thread pool, and then accept and execute work in order. This mode can reduce resource consumption when creating threads, and can also control the amount of resources available by adjusting the number of waiting threads. This chapter will also introduce the thread processing methods of AWT and Swing (JFC), and give a sample program that uses the thread pool through the java.util.concurrent package.
Chapter 9 "Future Mode-Give You a Bill of Lading" will introduce the Future Mode. In this mode, the results of tasks assigned to other threads can be obtained synchronously. This mode is suitable for calling asynchronous methods. In addition, this chapter will give sample programs of java.util.concurrent.Future, FutureTask and callable.
Chapter 10 "Two-Phase Termination Mode-Clean up the room before going to sleep" will introduce the Two-Phase Termination mode used to terminate threads. This mode can use appropriate termination processing to safely terminate the thread. This chapter will also introduce the interrupt handling of threads and give sample programs of CountDownLatch and cyclicBarrier in the java.util.concurrent package.
Chapter 11 "Thread-Specific Storage Mode-One Thread, One Locker" will introduce the Thread-SpecificStorage mode. In this mode, each thread will have its own variable space. When using this mode, the variable space between multiple threads is completely separated, so there is no need to perform mutual exclusion processing. This chapter will also introduce how to use java. lang. ThreadLocal class.
Chapter 12 "Active Object Mode-Active Object Receiving Asynchronous Messages" will introduce the Active Object mode. In this mode, the program creates active objects. The active object will receive external messages and hand them over to its own thread for processing. When using this mode, method invocation and method execution are separated from each other. This chapter will also give sample programs that use the classes in the java.util. concurrent package.
Chapter 13 "Summary of a Pattern Language for Multithreaded Programming" will use the form of a pattern language to summarize the relationship between the 12 patterns introduced in this book.
algorithm
Algorithms are also going crazy now. If you don’t brush "Sword Finger Offer" again, and if Leetcode brushes one or two hundred common questions, you dare to go to an interview with a big factory. It is already 5 years ago, and you will only be tested in a quick queue. There have been too many programmers in the past few years, such as mergers, and it’s impossible to say that it’s impossible to say that it’s impossible to say that it’s impossible to say that there are too many programmers. I used to boil frogs in warm water before, and I was taught various ways to behave after going out for an interview! For example, in the previous interview with an AI unicorn, the first two sides were almost all algorithmic questions, and you didn't ask much else. If you don't prepare, you will almost 100% hang up.
From my previous interview experience, the difficulty of algorithmic interviews has increased significantly in recent years. Not only large factories, but even many small and medium-sized factories also directly leetcode the original question. If you are lucky, I will ask you easy. If you are not lucky, you may even start directly from medium/hard. The interview style of big companies is more and more in line with North American companies.
Algorithm book recommendation
"Programmer Code Interview Guide: The Optimal Solution of IT Famous Companies' Algorithm and Data Structure Problems"
There are many good algorithm books, but the algorithm books explained in Java language seem to be the only one that is relatively good;
(This algorithm book of Zuo Shen only needs to like + follow and add ↓↓↓ to get the PDF version for free)
This is a programmer interview book! The book summarizes the best solutions to various questions in the code interviews of well-known IT companies and provides related code implementations. Aiming at the current pain point of the lack of authoritative questions in programmer interviews, this book selects nearly 200 classic code interview questions that have actually appeared to help programmers prepare for the interview without fail. After "brushing" the book, you are the "king of inscription"! __eol__ This book organizes the content in the way of questions + answers, and puts the questions with similar types of interview questions or similar solutions together as much as possible. When reading this book, readers can easily see the connection between the interview question solutions and enable knowledge learning Avoid fragmentation. The book divides all interview questions from difficult to easy into four grades of "general, school, lieutenant, and scholar", so that readers can choose "brush" questions in a targeted manner. All the interview questions included in this book give the best explanation and code implementation, and provide some running time comparisons between common and optimal solutions, so that readers can truly feel the charm of optimal solutions! __eol__ The topics in this book are comprehensive and classic. More importantly, the book contains a large number of exclusive topics and optimal solution analysis, which are derived from the author's in-depth thinking of "deadly smashing myself" for many years. __eol__ Coders, are you ready to stand out and become famous in the interview with famous IT companies? This book is the "great weapon" you should have. Of course, for programmers who need to improve their ability in algorithms and data structures, the value of this book is also obvious.
I won't introduce it bit by bit due to space reasons, let's take a cut of the catalog diagram and feel it;
Microservice
"Microservice Architecture Actual Combat"
The current status of microservices is that there are more concepts than practices. Managers and architects often don’t know how to implement microservices. This book starts from the perspective of software engineering and incorporates the author’s years of management and architecture experience. The content is completely based on actual experience. Sore spot. By reading this book, developers can realize the rapid landing of microservices.
The book has 12 chapters, divided into concept chapters, development chapters, operation and maintenance chapters and actual combat chapters. The concept article elaborates on the origin and design points of microservices. The development chapter introduces the application of Spring Boot, Docker and Spring Cloud to microservices, and attaches source code. The operation and maintenance chapter introduces the knowledge points involved in microservices from the perspective of testing, rapid development, quality management, automated operation and maintenance and monitoring. The actual combat article lists the content involved in enterprise-level development as detailed as possible.
Friends who need this "Microservice Architecture Practical Combat" manual can get it for free by just clicking like + commenting and adding the end of the article;
brief introduction:
Chapter 1: Explore microservices from the perspective of the origin of microservices and the actual business, so that readers can have a perceptual understanding of microservices.
Chapter 2: It is to organize the design concepts of microservices, including how to divide services, separation of front and back ends, CAP theory and CQRS, etc., which is a high-level guiding principle.
Chapter 3: A detailed introduction to the development of Spring Boot, including the advantages and disadvantages of using it, and the integration of toolkits commonly used in enterprise-level development, including aspect-oriented programming, Web development, document management and scheduling management, and finally completed with Dubbo An exemplary distributed project.
Chapter 4: Mainly explain the basic operations of Docker, introduce the container-related technologies used in microservices, and finally give a general container-based private cloud architecture.
Chapter 5: Describe several important frameworks for Spring Cloud to implement microservices, so that readers can understand the registry, load balancing, fault tolerance, distributed configuration, gateway and message bus, and can complete the microservice architecture at the development level.
Chapter 6: An introduction to Spring Cloud's non-core frameworks, including Consul, ZooKeeper, security framework, and data flow framework.
Chapter 7: Mainly introduces testing and quality management. The testing part includes unit testing, AB testing, smoke and regression testing. The quality management part mainly uses static code analysis, and statically checks the code based on SonarQube, and analyzes the code. Overall quality.
Chapter 8: A systematic introduction to the best practice of microservices, JHipster, and some processing of JHipster. The parts that are not very popular in China are processed, and the application and configuration of JHipster are introduced in detail as much as possible.
Chapter 9: Mainly introduces automated deployment, because the purpose of microservices is not only to simplify development, but also to improve the efficiency of the entire team. Therefore, the use of private servers and automated operation and maintenance are very important.
Chapter 10: Mainly explains log collection and APM monitoring. For online systems, the probability of problems is still very large. How to quickly locate and find the point of the problem in the first time is very important. The APM part lists commonly used monitoring tools, focuses on Pinpoint, and focuses on usage and email alerts.
Chapter 11: Through a comprehensive explanation of PiggyMetrics, readers can understand the technical points and construction principles of a simple microservice architecture, and actually deploy microservices to complete the basic operations of the business.
Chapter 12: Explain the technical points that may be involved in the construction of microservices, including workflow engine, rule engine, scheduling system, distributed configuration, and single sign-on.
Directory overview:
Write at the end
The above are the three books recommended by the editor. I hope it will be helpful to everyone in the interview. I wish you all can find a happy job!
The name of the data is [Multithreading + Algorithm + Microservice]
