Hangzhou – Ali Cloud -Java intern
- Difference between a List and a Set
- How is a HashSet guaranteed not to repeat itself
- Is HashMap thread safe, and why not?
- Expansion process of HashMap
- What is the difference between HashMap 1.7 and 1.8?
- final finally finalize
- Four kinds of references to objects
- Java gets reflection in three ways
- Java reflection mechanism
- Arrays.sort and collections. sort
- The application of LinkedHashMap
- Cloneable interface implementation principle
- Exception classification and handling mechanism
- The difference between ‘wait’ and ‘sleep
- How are arrays allocated in memory
Hangzhou – Ant Financial -Java Advanced
1. What has changed between JDk1.7 and JDk1.8 Map (bottom level)?
2. ConcurrentHashMap
3. What is the difference between parallelism and concurrency?
4. What changes have taken place between jdk1.7 and jdk1.8 Java virtual machines?
5. If you were asked to design middleware yourself, how would you do it?
6. What is middleware?
7. Have you used ThreadLock before? What does it do?
8. What is the difference between Hashcode () and equals ()?
9. When is an index set in a mysql database but cannot be used?
Mysql optimization will not,mycat branch, vertical branch, horizontal branch?
11. Distributed transaction solution?
12 SQL statement optimization will not, say what you know?
Mysql storage engine
14. Red black Tree principle?
Hangzhou – Ant Financial – Senior Engineer
Ant Java side
1. What is the relationship between binary search tree and balanced binary tree, strongly balanced binary tree (AVL tree) and weakly balanced binary tree
What’s the difference
MySQL > use B+ tree; MySQL > use B+ tree
3. How does HashMap resolve Hash conflicts
4. Differences between epoll and poll and their application scenarios
5. Describe the thread pool principle. What is the blocking queue used by FixedThreadPool?
6. Difference between sychronized and ReentrantLock
7. Sychronized spin locks, bias locks, lightweight locks, and heavyweight locks are introduced and related respectively
8. What are the problems of HTTP, what are the encryption algorithms, and the problems that may arise for different encryption methods, and
How does HTTPS ensure secure transmission
Ant Java 2 side
1. What are the major categories of design patterns and be familiar with them
2. How does volatile ensure visibility and order
3. Java memory structure, which parts of the heap are divided into, and the default age of the old age
4. How does ConcurrentHashMap keep threads safe? What are the changes in JDK1.8
5. Why red black tree at the bottom of ConcurrentHashMap
6. How to do MySQL optimization
7. Tell me about OOM and how to deal with this situation. Have you used log analysis tools
Ant Java three sides
1. Project introduction
2. How do you ensure data consistency between Redis cache and database?
3. Redis cache avalanche? The breakdown? Pass through me?
4. Which message-oriented middleware are you familiar with and have you done performance comparisons?
Nanjing – Isoftstone -Java elementary
1. Where can the lock be locked?
2. How to use reflection to get objects in a class?
3. The difference between HTTP and HTTPS?
4. Tell me what you know about TCP/IP
Talk about the application of Aop and IOC
Are Spring beans thread-safe?
7, Maven package and install difference
8. What design patterns have you encountered?
9. Talk about the difference between a simple factory and an abstract factory
10. Tell me about the basic Linux commands you use
11. Talk about the expansion mechanism of Currenthashmap
Xiamen – Chinasoft International -Java Primary
The difference between equals and hashCode in Java
2, int, char, long how many bytes each
3, the difference between int and integer
4, talk about the understanding of Java polymorphism
5, String, StringBuffer, StringBuilder
What is an inner class? The role of inner classes
7. Distinction between abstract classes and interfaces
7.1. The meaning of Abstract Classes
7.2 Application Scenarios of Abstract Classes and Interfaces
7.3. Can abstract classes have no methods and attributes?
7.4. Meaning of interfaces
8. The difference between extends and super in generics
Can a static method of a parent class be overridden by a subclass? Can static properties and methods be inherited?
The difference between a process and a thread
11. Final, finally, Finalize
Serializable and Parcelable differences
Talk about your understanding of Kotlin
14. The method and principle of converting string into INTEGER
Shanghai – Pinduoduo -Java Advanced
1. Three elements of concurrent programming?
2. What are the ways to achieve visibility?
3. The value of multithreading?
4. What are the ways to create threads?
5. How do you compare the three ways to create threads?
6. Thread state flow diagram
Java threads have five basic states
What is a thread pool? What are the ways to create it?
9. Create thread pools:
10. What are the advantages of thread pools?
11. What are the common concurrency utility classes?
12. CyclicBarrier and CountDownLatch
13. The role of synchronized?
14. The role of the volatile keyword
15. What is CAS
16. CAS
17, What is Future?
18. What is AQS
19. AQS supports two synchronization modes:
20. What is ReadWriteLock
21. What is FutureTask
The difference between synchronized and ReentrantLock
What is the optimistic lock and pessimistic lock
24. How does thread B know that thread A has changed A variable
25. Comparison of synchronized, volatile and CAS
What’s the difference between sleep and wait?
27. What is ThreadLocal? What’s the use?
28. Why wait() and notify()/notifyAll() are called in synchronized blocks
What are the methods of multithreading synchronization?
Thread scheduling policy
31. What is the concurrency of ConcurrentHashMap
How do I find which thread uses the longest CPU in Linux
Java deadlocks and how to avoid them?
The cause of the deadlock
How do I wake up a blocked thread
36. How does immutable objects help multithreading
What is multithreaded context switching
38. What happens if the thread pool queue is full when you submit a task
39. What is the thread scheduling algorithm used in Java
What are Thread schedulers and TimeSlicing?
What is spin
Concurrency Is the Java Concurrency API. What is the Lock interface? What are the advantages over synchronizing it?
Singleton thread safety
44. What does Semaphore do
Executors: What are they?
Thread class constructor, static block is called by which thread
Shanghai – Ctrip -Java advanced
1. Describe how the JVM loads Class files.
2. What is a class loader?
3. What are class loaders?
4. What is the Tomcat class loading mechanism?
Class loader parent delegate model mechanism?
Java memory allocation?
7. What is the structure of the Java heap?
8. Describe the changes in the memory area of each version.
9. What is the role of each region?
10. Is there a memory leak in Java?
11. Java class loading process?
12. What is GC? Why GC?
13. What is the Java garbage collection mechanism?
14. How do I determine if an object is alive?
15. What are the advantages and principles of garbage collection and consider the two recycling mechanisms? What is the rationale?
16. Deep copy and shallow copy?
17. What is Distributed Garbage Collection ( DGC)? How does it work?
Shenzhen -OPPO-Java Advanced
1. Tell me about your work experience.
2. Which modules are the project mainly responsible for?
3. Map out the structure of your project
4. How does Eureka register its services?
5. What will Eureka do if the service is down or inaccessible and I still request the service? What would happen?
6. Talk about Eureka’s protection mechanism
7. Is the Ribbon’s load balancing service internal or external?
8. How does the Ribbon achieve load balancing?
9. If THERE is no Eureka, can I directly make service requests through the Ribbon?
10. How does Hystrix achieve circuit breaker?
11. When the service is inaccessible, is it a direct circuit breaker or a downgrade?
12. How can circuit breakers occur?
13. What is the process for consumers to invoke providers in Springcloud? Draw a picture of how SpringCloud works
14. What are the clustering methods of Redis?
15. If you read data in Redis and its data structure changes, how to process it without changing the code, so that the downstream business will not be affected?
16. What are the persistence methods of Redis? Talk about their implementation,
17. Do you have any problems when using Redis?
18. What are the memory reclamation mechanisms of Redis?
19. What are Redis expiration strategies? A little bit about the different strategies
20. What is Redis’ elimination strategy? Can obsolete algorithms be modified or rewritten?
21. What is the message-oriented middleware used in your project?
22. How is your Rabbit cluster deployed?
23. How is data synchronized between Rabbit clusters? Synchronous or asynchronous?
24. Do you store the data in a queue on one machine or multiple machines? Why is that?
25. What is the internal structure of RabbitMQ? Please draw the RabbitMQ architecture diagram
26. Is there a separate table for your company’s database? How is it done?
27. What is the index of Mysql based on?
28. Talk about B+ trees
29. What is the difference between using an autoincrement ID and a UUID as the primary key?
30. What are the transaction isolation levels of the database?
31. How do we implement transactions in code?
32. Is there a problem if the code business flow is long in a transaction? Why does this happen?
33. Have you had any problems using the volatile keyword? Why does this question arise?
34. Talk about the underlying implementation of volatile
35. How do I create a thread pool? What are the parameters? Implementation principle of thread pool
36. Do you have any questions for us?
Shenzhen – Fengchao Technology -Java advanced
1. Differences between BIO and NIO
2. The difference between poll and select
3. Working principle of ZooKeeper
4. The theory of the cap
5. Which two theories are satisfied by the two-paragraph formula of CAP theory
6. Thread pool parameter configuration, why does Java officially provide factory methods for thread pool
7. The benefits of distributed framework Dubbo, can not use Dubbo. Why use distributed
8. How can seven garbage collectors be used together
9. Traffic limiting solution for interfaces
10. Working principle of ConcurrentHashMap
11. Map concurrency solution
12. What is a coroutine and how to implement it
Implementation of LRU cache using Hash Map
14. Depth and breadth traversal of graphs (algorithm)
15. Basic Sorting (Algorithm)
16. Use of design patterns
Java 8 streaming usage
18. What about b+ trees?
19. Memory barriers and volatile:
20. The concept of Java domains
21. Concept of distributed design domain
22. How to realize shopping flow limiting on Double 11 (Redis implementation scheme)
23. Mysql tuning
24. CDN (Live more in different places)
25. Communication between processes
26. TCP/IP and HTTP
Write a redis distributed lock:
28. Spring’s seven transaction propagation behaviors:
29. Processing Scheme of distributed Down Machine (Heartbeat Detection)
30, the analysis of distributed strong consistency, weak consistency, final consistency?
31, Dubbo and Zookeeper as the difference between the registry, if the registry is down, can consumers still call the service, with what call
32. Schematic diagram of Dubbo (draw the relationship between registry, consumer and producer, and say the role of each role)
33. Is multithreading used in the project?
34. Basic principles of HashMap (including underlying data structure and how to expand capacity)
35. Principle of ConcurrentHashMap
Implementation of distributed lock
37. Distributed session, how to keep consistent
What message-oriented middleware uses and their differences
1. We know that hashMap threads are not safe, so what class can replace them to keep them safe? How do they achieve thread-safety?
2. How many GC mechanisms are there?
3. What about consistency hash?
4. Basic knowledge of Mybatis;
5. Mysql basic knowledge;
6. How much data does mysql express in a single database?
7. Hibernate basics.
8. Tell us how Kafka works. Why does it guarantee such high throughput?
9. What do you know about WebService?
10. Tell me about your git branch management scheme?
11. How to divide mysql into tables and libraries?
12. How do you interconnect with the front end?
13. Tell me about a major problem or challenge you have faced and how you went about solving it. Focus on solutions to the company’s online problems.
Shenzhen – Le Xin -Java advanced
1. Draw the project architecture diagram
2. What technical points are used in the business module I am in charge of?
3. How to achieve the final consistent distributed transaction?
4. What is the B+ tree structure of the index?
5. Under what circumstances will indexes fail? What other ways are there to optimize queries besides indexing?
6. What design patterns do you know? What design patterns are used in Spring? Have you used any design patterns?
7.TCP three-way handshake and four-way wave?
8. Https principles?
9. What are the data types of Redis? How is it different from Memcached?
10. Is the message queue useful? How is it used in the project? How to ensure the reliable delivery of messages?
1. Talk about Java collections. What implementation classes and data structures are under each collection?
2. Introduce red-black tree and binary balanced tree.
3. In JDk1.8, ConcurrentHashMap is converted to a red-black tree if its size is greater than 8.
What locks are available in Java? What are the characteristics of each lock?
5. Talk about how volatile ensures visibility, from the CPU level.
6. The order in which Spring loads beans?
7. Which objects will be stored in the old age?
8. When does the full GC trigger?
9. Where does oom appear in the JVM? What are the possible reasons for oom?
10. How do we find out which region of the JVM oom comes from?
11. Have any JVM tuning experience? What are the tuning options?
12 have you read any source code at ordinary times, please draw it.
13. Have you ever written or seen a Custom ClassLoader?
14. Describe a recent project you worked on, drawing the framework and analyzing the business process.
15. Which books do you read?
Shenzhen – Sensetime -Java Advanced
1. Ask what you write in your resume, and pay attention to the similar product ecology and comparison of the technology used.
2. Kafka data partition and consumer relationship, kafka data offset reading process, kafka internal how to ensure the order, combined with external components how to ensure the order of consumers
3. CMS garbage collection mechanism
4. Functions of each component of SpringCloud, internal details, differences from Dubbo, Dubbo architecture, duBBo load strategy
5. Graphs theory
Nio, Bio, Sellector /epoll, AIO, Netty built-in codec, Netty Advantage, Java memory model
7. Akka model
8. Java ArrayList, linkedList, HashMap and ConcurrenthashMap, ConcurrenthashMap 1.7 and 1.8,
Implementation details, linkedhashMap sorting principle, application how to ensure data idempotent
Web. XML Listener, filter, servlet loading sequence. How to load a filter without configuration in Web, XML
10. Infinite number provides multiple solutions to the top K problem
11. A, B, C three tables, do associative query, how to optimize, can do foreign key, only add a table C foreign key can be.
What is the difference between CourrentHashMap JDK1.7 and JDK1.8?
13. Threads A, B, C, and D run tasks. How to ensure that threads A, B, and C finish executing tasks before thread D?
14. How to ensure data consistency in distributed system?
15. Where and how to split microservices?
16. What components do SpringCloud family buckets contain?
17. Have you learned about Docker? What is the difference between Docker and virtual machine?
18. How to communicate between multiple Docker containers in the same host? How do Docker containers communicate among multiple hosts?
19. How to optimize the performance of high concurrency system? How to prevent oversold inventory?
20. How to ensure service idempotency?
Shenzhen – Yinsheng Payment -Java Intermediate
1. Talk about how SpringCloud works
2. What components are used to send requests
3. The registry heartbeat is seconds
4. How do consumers discover service providers
5. What is the default allocation method of Eruka when multiple consumers call the same interface
6. What are the common SpringBoot annotations and their implementation?
7. What are Spring’s transaction annotations? When do things roll back
8. Talk about the spread and isolation levels of Spring things
9. What is the mysql engine? Their differences
10. How does InnoDB implement mysql transactions
Mysql > select * from ‘mysql’
12. Talk about how B + trees work
13. If you were asked to design an index, what would you do
What is the difference between Git and SVN
15. Some underlying principles and processes of git commands
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Interview questions and answers overview
