The gospel of programmers! Summary of top ten Java technology points that are the first choice for advanced architects

Opening:

As a Java programmer, do you usually get stuck in business development? Every day , you are busy typing code, system development, bug modification, and feel like you are omnipotent. However, at an occasional party, I heard that my classmates who debuted with me already had an annual salary of 500,000, but I was shy in the pocket. So I also want to see new opportunities, find a new platform, and develop well.

But during the interview, when the smiling interviewer asked those familiar Java questions, he just felt familiar, but couldn't answer it. For example, the working principle of HashMap, or the usage scenarios of volatile.

At this time, I began to doubt my abilities, and hated why I didn't review it well in the first place.

Frankly speaking, as a Java veteran, from my point of view, some interviewers do work hard, but the level of ability shown is not enough to pass the interview or get a high salary . I think there are usually two reasons:

 

• ⊙  First, "knowing what is happening and not knowing why." I have been working on technology for many years and have developed many business applications, but it seems that I have not considered the logic behind various technology choices . Therefore, I am not assured of entrusting him with tasks with a certain depth. More importantly, I am not sure about the growth potential of his future technical capabilities.

 

• ⊙Second  , knowledge is fragmented and unsystematic. In the interview, the interviewer seemed unable to completely and clearly describe the system he developed or the related technology used. Therefore, I would doubt whether he has the ability to efficiently solve complex problems and design complex systems.

If you usually work hard, or go too far on certain implementation details, but haven't looked up at these technologies, you must pay attention. When preparing for an interview, you need to sort out the Java knowledge system and summarize the core and key points in order to draw inferences and talk about it when facing different interviewers.

The following is a summary of the technical knowledge, interview topics and answers for some Internet company java programmer interviews, hoping to help friends who want to change jobs after the year to find a job that they are satisfied with.

Technical knowledge to be prepared

The following are the interview questions that are frequently asked in these interviews, but these questions are just the tip of the iceberg. Even if they are all, they can’t do anything. The most important thing is a solid foundation and a clear mind.

Essential for Java

1. The difference between HashMap, HashTable and ConcurrentHashMap.
2. The difference between ArrayList and Vector.
3. Talk about the storage performance and characteristics of ArrayList, Vector, LinkedList.
4. What is the difference between fail-fast and fail-safe?
5. The data structure of hashmap.
6. How does HashMap work?
7. When will Hashmap expand?
8. How to optimize HashMap in DK8.
9. What are the characteristics of the three interfaces of List, Map, and Set when accessing elements?
10. Two ways of dynamic proxy, and the difference.
11. The @transactional annotation will be invalid under what circumstances and why.

Algorithm and data structure

1. B+ tree
2. Quick sort, heap sort, insertion sort (all eight sorting algorithms should be understood)
3. Consistent Hash algorithm, the application of consistent Hash algorithm

JVM performance optimization

1. Java memory allocation?
2. What is GC? Why is there a GC?
3. Briefly describe the Java garbage collection mechanism. What is the basic principle of the garbage collector?
4. What is distributed garbage collection (DGC)?
5. The process of Java class loading? Parent delegation mechanism?

 

Multithreading and concurrency

1. What is multi-threaded concurrency and parallelism? What is the thread safety issue?
2. What are reentrant locks, optimistic locks, pessimistic locks, fair locks, unfair locks, exclusive locks, and shared locks?
3. Tell me about the implementation principle of ThreadLocal? How does ThreadLocal act as a thread isolation method for variables?
4. The principle of exclusive lock ReentrantLock? The principle of ReentrantReadWriteLock?
5. The principle of ConcurrentLinkedQueue, a non-blocking unbounded queue based on a linked list?

 

Database related

1. Please briefly describe the names of the four transaction isolation levels supported by InnoDB in MySQL and the differences between each level?
2. What storage engine is used in MySQL? What kind of locks are there in MySQL?
3. What is MongoDB? MongoDB features? What is the function of MongoDB? Where is MongoDB applicable?

 

Network protocol

1. Talk about the difference between TCP and UDP?
2. Three handshake, four waves? Why do you wave your hands four times?
3. What is the problem of sticky and half-packed? Why do sticky and half-packed occur? How to avoid sticky and half-packed problems?

 

Design Patterns

1. J2EE commonly used design patterns? Explain the factory model?
2. Which design patterns are used in development? In what occasions?

 

Distributed and middleware

1. What are the load balancing algorithms of zookeeper?
2. Do you use distributed scenarios in your business? Session distributed solution?
3. The scenario of distributed locks? Distribution is the realization of locks?
4. Distributed transaction? Clustering and load balancing algorithm and implementation?
5. Sub-database and sub-table design? Distributed dilemmas brought by sub-database and sub-table and countermeasures?

 

 

 

Cache related

1. What is the difference between Redis and memcached? What data structure does Redis support?
2. Is Redis single-threaded? Is all work single-threaded?
3. How does Redis store a String? Redis deployment method, master-slave, cluster?
4. In the sentinel mode of Redis, how can a key value be found and stored in a Redis cluster? Redis persistence strategy?

 

Source code framework related

1. What is the Spring framework? What are the main modules of the Spring framework? What is Inversion of Control (IOC)? What is dependency injection?
2. What is the difference between BeanFactory and ApplicationContext?
3. Briefly talk about the workflow of Spring MVC.
4. How to use @ModelAttribute? Talk about your understanding of custom data type converters.
5. What is the interface binding of MyBatis and what are the benefits?

 

to sum up

No matter which company it is, it attaches great importance to high-concurrency and high-availability technologies, basics, and JVM. The interview is a two-way selection process. Don't go to the interview with a fearful attitude, which is not conducive to your own performance. At the same time, you should not only pay attention to salary, but also whether you really like this company and whether you can really get exercise. In fact, writing so much may not apply to everyone. I believe that after some interviews, everyone will have these feelings. If these can help you, then the best!

The outline of Java interview technical points, the real interview questions and the analysis materials of the Java interview questions from major manufacturers are given to friends for free

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