Java back end test questions

1, The difference between List and Set

2. How is a HashSet guaranteed to be non-repetitive

3. Is HashMap thread safe, and why not?

4. Expansion process of HashMap

5. What are the differences between HashMap 1.7 and 1.8?

6. Four references to objects

Java gets reflection in three ways

Java reflection mechanism

9, Arrays. Sort and collections. sort

10. LinkedHashMap application

11. Implementation principle of Cloneable interface

12. Anomaly classification and processing mechanism

What is the difference between ‘wait’ and ‘sleep’

How are arrays allocated in memory

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Kafka interview topics and answers

1. What is Kafka designed for?

2. What are the three definitions of data transmission?

3. What two conditions does Kafka have to determine if a node is alive?

4. Does the producer directly send data to the broker’s leader?

Can Kafa consumer consume partitioned messages?

Do Kafka messages use Pull mode or Push mode?

7. What is the message format Kafka stores on hard disk?

Kafka efficient file storage design features:

9. There are three key differences between Kafka and traditional messaging systems

How does Kafka create topics to place partitions into different brokers

Kafka partition will be created in the directory

12. How to save data on a partition to a hard disk

Kafka’s ACK mechanism

14. How do Kafka consumers consume data

Consumer load balancing strategy

16. Data is ordered

Kafaka is a grouping policy for producing data

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Redis interview topics

1. What is Redis? Describe its advantages and disadvantages.

What are the advantages of Redis over memcached?

3. What data types does Redis support?

4. What physical resources do Redis mainly consume?

5. What kinds of data elimination strategies does Redis have?

6. Why doesn’t Redis officially provide Windows version?

7. What is the maximum capacity of a string value?

8. Why does Redis need to put all data in memory?

9. What should Redis cluster solution do? What are the options?

10. When will Redis cluster solution make the whole cluster unavailable?

MySQL has 2000W data, redis only 20W data, how to ensure that redis data is hot data?

12. What are the suitable scenarios for Redis?

What are the Java clients supported by Redis? Which is the official recommendation?

14. What does Redis have to do with Redisson?

15. What are the advantages and disadvantages of Jedis versus Redisson?

Redis hash slot

17. What is the master/slave replication model of Redis cluster?

Will Redis write operations be lost? Why is that?

19. How are Redis clusters replicated?

What is the maximum number of nodes in a Redis cluster?

21. How to select database for Redis cluster?

22. What is the use of pipes in Redis?

23, How to understand Redis transaction?

What are the Redis transaction related commands?

25. How to set the expiration time and permanent validity of Redis key respectively?

26, Redis how to do memory optimization?

27. How does the Redis recycle process work?

28. Locking mechanism

Lock mutual exclusion mechanism

30. Automatic delay mechanism of Watch Dog

31. Reentrant locking mechanism

Release lock mechanism

33. Disadvantages of Redis distributed lock

Have you ever used Redis distributed lock? How is it implemented?

Have you ever used Redis for asynchronous queues? How do you use it? What are the disadvantages?

What is cache penetration? How to avoid it? What is cache avalanche? How to avoid it?

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What’s the difference between Redis and memcached? Why is single-threaded Redis sometimes more efficient than multi-threaded memcached at high concurrency?

How is master slave replication implemented in Redis? How is the redis cluster model implemented? How is redis key addressed?

How to design distributed locks using Redis? What is the implementation idea? Is zK ok? How to do that? What’s the difference between the two?

Do you know the persistence of Redis? How is this implemented at the bottom? What are the advantages and disadvantages?

41. What are redis expiration strategies? Do you know the LRU algorithm? Write the Java code implementation?

Cache penetration, cache breakdown, cache avalanche solution?

43. When selecting cache, when to select Redis and when to select memcached?

What if the cache is inconsistent with the database?

45. How to solve the inconsistency between master and slave databases?

46, Redis common performance problems and solutions

47. What are Redis data elimination strategies?

What are the data structures in Redis?

49. If there are 100 million keys in Redis and 10W of them start with a fixed known prefix, how can we find them all?

Have you ever used Redis to do asynchronous queue? How is it implemented?

51. How does Redis realize delay queue?

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Micro service interview topics and answers

1. How is the separation of front and rear ends done

2. What are the frameworks of microservices

3. Talk about the implementation principle of RPC

4. Talk about how Dubbo works

5. How to understand RESTful

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Most comprehensive JVM interview topics

1. Memory model and partition, need to detail what to put in each partition.

2. Partitions in the heap: Eden, Survival (from+ to), old age, their respective characteristics.

3. Object creation method, object memory allocation, object access location.

4. Two determination methods of GC:

5. What is SafePoint

6. Principles and characteristics of GC’s three collection methods: mark clearing, mark sorting and copy algorithm are respectively used

Where would you like to optimize your collection methods?

7. What are the GC collectors? Features of CMS collector and G1 collector.

8. When will the Minor and Full GC occur?

9. Several common memory debugging tools: Jmap, JStack, JConsole, jhat

10. Several processes of class loading:

11. What are the partitions of THE JVM memory, and what is the purpose of each partition?

12. For example, and determine whether an object is alive? (or GC object determination method)

13. How about Java garbage collection?

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

15. Java memory model

16. Java class loading process?

17. What is the Java class loading mechanism?

Class loader parent delegate model mechanism?

19. What is a class loader and what are class loaders?

20. Briefly describe the Java memory allocation and reclamation policy and the Minor and Major GC

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