The latest "Ali" Java senior engineer interview high-frequency questions in 2023: JVM+Redis+ concurrency + algorithm + framework

foreword

Facing this year's general environment, the difficulty of job-hopping success is much higher than in previous years. The obvious feeling is: For this year's java development friends job-hopping interview, no matter one side or two sides, they will start to test the technical skills of a Java programmer. and foundation. The interpretation of the source code and the understanding of the core principles have also become bonus items, especially the interview of friends who do not have enough knowledge of some core basic knowledge points of Java or have no system direction has become a distressing thing.

Today I am here to share the frequently asked questions in Java interviews in domestic companies, including JVM, commonly used algorithms and data structures, redis cache, distributed, Spring, microservices, etc. As the saying goes, knowing yourself and the enemy, only when the system knowledge is consolidated, can you quickly master the constantly updated technology, and at the same time stand out in interviews and work!

Due to space reasons, I will not show all the answers here. I have compiled these questions into pdf documents and shared them with friends in need for free. At the same time, it took a lot of time to sort them out. Friends in need can think about them in the background [717 ] can

300 Frequently Asked Java System Interview Questions

Java Collections 22 questions

1. The difference between ArrayList and Vector.

2. Talk about the storage performance and characteristics of ArrayList, Vector, LinkedList.

3. What is the difference between fail-fast and fail-safe?

4. The data structure of the hashmap.

5. How does HashMap work?

6. When will Hashmap be expanded?

7. What are the characteristics of the three interfaces List, Map, and Set when accessing elements?

8. The elements in the Set cannot be repeated, so what method is used to distinguish whether it is repeated or not? Is it == or equals()? What is the difference between them?

9. Two objects have the same value (x.equals(y) == true), but they can have different hash codes. Is this correct?

10. What is the difference between heap and stack.

11. What are the basic interfaces of the Java collection class framework?

12. What is the difference between HashSet and TreeSet?

13. What is the underlying implementation of HashSet?

14. What is the implementation principle of LinkedHashMap?

15. Why does the collection class not implement the Cloneable and Serializable interfaces?

16. What are Iterators?

17. What is the difference between Iterator and ListIterator?

18. What is the difference between an Array (Array) and a List (ArrayList)? When should you use Array instead of ArrayList?

19. What are the best practices for Java collection class frameworks?

20. The elements in the Set cannot be repeated, so what method is used to distinguish whether it is repeated or not? Use == or equals()? How do they differ?

21. What are the Comparable and Comparator interfaces for? list their differences

22. The difference between Collection and Collections.

JVM and Tuning 21 questions

1. Java class loading process?

2. Describe the principle mechanism of JVM loading Class files?

3. Java memory allocation.

4. What is GC? Why is there GC?

5. Briefly describe the Java garbage collection mechanism

6. How to judge whether an object is alive? (or the judgment method of the GC object)

7. The advantages and principles of garbage collection. and consider 2 recycling mechanisms

8. What is the basic principle of the garbage collector? Can the garbage collector reclaim memory immediately? Is there any way to actively notify the virtual machine to perform garbage collection?

9. Will there be a memory leak in Java, please describe briefly

10. Deep copy and shallow copy.

11. What do System.gc() and Runtime.gc() do?

12. When is the finalize() method called? What is the purpose of a destructor (finalization)?

13. If the object's reference is set to null, will the garbage collector immediately free the memory occupied by the object?

14. What is Distributed Garbage Collection (DGC)? How does it work?

15. What is the difference between a serial collector and a throughput collector?

16. In Java, when can an object be garbage collected?

17. Briefly describe Java memory allocation and recovery strategies, Minor GC and Major GC.

18. Does garbage collection happen in the permanent generation of the JVM?

19. What are the methods of garbage collection in Java?

20. What is a class loader and what are the class loaders?

21. Class loader parent delegation model mechanism?

Concurrent Programming 28 questions

1. Have you ever used Synchronized, what is its principle?

2. You just mentioned acquiring a lock on an object, what exactly is this "lock"? How to determine the object's lock?

3. What is reentrancy, why is Synchronized a reentrant lock?

4. What optimizations does the JVM make to Java's native locks? 48

5. Why is Synchronized an unfair lock? 49

6. What are lock elimination and lock coarsening? 49

7. Why is Synchronized a pessimistic lock? What is the implementation principle of optimistic locking? What is CAS and what are its features?

8. Is optimistic locking necessarily good?

9. Compared with Synchronized, what is the difference in the implementation principle of ReentrantLock?

10. So please talk about the AQS framework is going on?

11. Please compare the similarities and differences between Synchronized and ReentrantLock as detailed as possible.

12. How does ReentrantLock achieve reentrancy?

13. Besides ReetrantLock, which concurrency tools in JUC have you been exposed to?

14. Please talk about ReadWriteLock and StampedLock.

15. How to synchronize Java's threads with each other? What synchronizers do you know about? Please introduce them separately.

16. CyclicBarrier and CountDownLatch look very similar, please compare?

17. Java thread pool related issues

18. How is the thread pool implemented in Java?

19. How many core construction parameters are there to create a thread pool?

20. How are threads in the thread pool created? Was it created with the start of the thread pool from the beginning?

21. Now that it is mentioned that different thread pools can be created by configuring different parameters, what are the thread pools implemented by default in Java? Please compare their similarities and differences

22. How to submit threads in Java thread pool?

23. What is Java's memory model, and how do threads in Java see each other's variables?

24. Please talk about the characteristics of volatile, why it can ensure the visibility of variables to all threads?

25. Since volatile can guarantee the visibility of variables between threads, does it mean that operations based on volatile variables are concurrently safe?

26. Please compare the similarities and differences between volatile and Synchronized.

27. Please talk about how ThreadLocal solves concurrency safety?

28. Many people say that ThreadLocal should be used with caution. Tell me about your understanding. What should you pay attention to when using ThreadLocal?

Spring25 question

Microservice 58 questions (SpringBoot, SpringCloud, Dubbo)

Netty10 questions

1. What is the difference between BIO, NIO and AIO?

2. What is NIO made of?

3. Netty features?

4. Netty's threading model?

5. Reasons and solutions for TCP sticky/unpacking?

6. What serialization protocols do you know?

7. How to choose a serialization protocol?

8. Netty's zero-copy implementation?

9. What are the performance aspects of Netty?

10. NIOEventLoopGroup source code?

network

1. Network 7-layer architecture

2. Principles of TCP/IP

3. TCP three-way handshake/four-way wave

4. HTTP principle

5. transfer process

6. HTTP status

7. Principle of CDN

Redis

1. What is redis?

2. Features of Reids

3. Data types supported by Redis

4. Redis is single-process and single-threaded

5. Virtual Memory

6. Redis lock

7. Read-write separation model

8. Data Sharding Model

9. Redis recycling strategy

10. What are the benefits of using Redis?

11. What are the advantages of redis over memcached? 4

12. Redis common performance problems and solutions

13. There are 2000w of data in MySQL, and only 20w of data in redis, how to ensure that the data in redis are all hot data245

14. What are the differences between Memcache and Redis?

15. What are the common performance problems of Redis? How to solve?

16. Scenarios where Redis is most suitable

Zookeeper，Kafka

Due to space reasons, I will not show all of them here. I have compiled these questions into pdf documents and shared them with friends in need for free. At the same time, it took a lot of time to sort them out. The way to get the materials for free is to think [717] in the background

All catalogs and answers are displayed, among which I have organized the data structure separately

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