Toutiao Tiktok Java (Three sides)

A:

  • Hashmap, how to expand, how to deal with data conflicts? How to efficiently implement data migration?
  • How to implement Linux shared memory
  • Socket network programming, say TCP three-way handshake and four-way wave
  • What is the difference between synchronous I/O and asynchronous I/O?
  • Java GC mechanism? What GC Roots do you have?
  • Red black tree, five features, insert and delete, time complexity?
  • What’s the time for quicksort, worst case, best case, heap sort, what’s the time for building the heap?

2:

  • Introduce yourself, what do you do and what are you good at
  • What do design patterns know?
  • How does AtomicInteger implement atomic modification?
  • Is ConcurrentHashMap different in Java7 and Java8? Why is Java8 more concurrency efficient? When do you use HashMap and when do you use ConcurrentHashMap?
  • Redis data structure?
  • Redis data elimination mechanism?

Three sides (about 50 minutes) :

  • Mysql Transaction Implementation principle (MVCC)
  • How to implement primary/secondary synchronization of MySQL data?
  • MySQL index implementation, innoDB index, b+ tree index is how to achieve, why use B + tree index node, how much data stored in a node, how to specify the size, and disk page corresponding?
  • If Redis has 100 million keys, will using keys affect online services?
  • Redis persistence mode, AOD and RDB, how to implement, append logs and backup files, the underlying implementation principle if you know?
  • What was the biggest difficulty? How to overcome it?
  • What are the plans for the future?
  • What did you want to ask me?

Advanced Java Development (One side + two sides + Three sides)

Meituan Side (Phone)

  • To introduce myself
  • Project introduction
  • Redis is introduced
  • Do you know the redis source code?
  • Do you know about redis clusters?
  • How does the back-end data structure shift when adding or deleting a Hashmap?
  • Why is the hashMap capacity a power of two?
  • The source code of hashset
  • Object class method that you know
  • The equals and hashcode
  • Have you overridden Hashcode and equals? What to look out for?
  • Suppose I have a student class that has a student id and a student name, and NOW when I rewrite the hashCode method, I just use the student id in the calculation, what happens? Put a student object into a set, change the student id of the student object, and then put it into a set. And say why
  • Persistence of Redis? What are the ways and how do they work?
  • Let’s talk about stable sorting algorithms and unstable sorting algorithms
  • Let’s talk about the idea of quicksort

Meituan Second Interview (Live)

  • To introduce myself
  • Let’s talk about acid of data
  • What is consistency?
  • What is isolation?
  • Isolation level of Mysql
  • How is each isolation level resolved?
  • Mysql > insert nextkey lock ();
  • Java’s memory model, garbage collection
  • Thread pool parameters
  • Explain each parameter once
  • The interviewer then sets each parameter, giving each thread a description of the process to be executed by the entire thread pool
  • What’s the difference between Nio and IO
  • Difference between Nio and AIO
  • How is Spring AOP implemented
  • What are the implementations of Spring AOP
  • Dynamic proxy implementation and differences
  • Does Linux understand?
  • How do I view system load?
  • If the Cpu load parameter is 4, describe the current system situation
  • Linux, find the largest file on the disk command
  • Linux, how to view system log files
  • Note: Given n pairs of Parentheses, write a function to Generate a new Parentheses combination and return the results of all the combinations.

Meituan Three Sides (Live)

They didn’t ask much about technology. They asked a lot of questions about technology management.

  • To introduce myself
  • Project introduction
  • How to manage project members?
  • How to communicate and convince development members when there is a disagreement, giving an example
  • How to ensure the project schedule?
  • The principles of database indexing
  • Non-clustered index and clustered index
  • Precautions for using indexes
  • Joint index
  • Explain the leftmost matching principle from the bottom
  • Is Mysql optimized for federated indexes? Will it automatically adjust the order? Which version starts tuning?
  • The application of Redis
  • Redis persistence method and principle
  • Technology selection, a new technology and a stable old technology, how will you choose, what are the considerations for choosing
  • Tell me your three most impressive meituan Dianping tech team blog posts
  • What new skills are you learning?
  • How do you get involved with a new technology?
  • What books do you read?
  • How to choose books to read?

Jingdong 4 (Java RESEARCH and Development)

One side (base: about 1 hour)

  • Introduce yourself, what do you do and what are you good at
  • Spring MVC is different from Spring-boot
  • @autowired implementation principle
  • What is the default scope of beans? Other areas of action?
  • What is an index and what does it do? What are the main index structures in MySQL? Hash index vs. B+ tree index?
  • How does a Java thread pool work? What are thread pools? What are the thread pool types in the thread pool factory, and what are their thread pool parameters?
  • The hashmap principle, which method is used to handle hash conflicts?
  • What else do you know about handling hash collisions?
  • Java GC mechanism? What GC Roots do you have?
  • How does Java do garbage collection? What objects age? What are the garbage collection algorithms? Why does the new generation use copying algorithms?
  • Time complexity of HashMap? How are Hash collisions resolved in a HashMap? What is the next level of the list? How has HashMap changed in Java8? Red-black trees need to compare sizes in order to insert. On what basis are they compared? Other Hash conflict resolution methods?
  • What’s the difference between a hash and a B+ tree? What scenarios do they apply to? Which is better?
  • Is there a difference between AES and MD5 for data security in the project? The detailed point

Second interview (ask more database)

  • To introduce myself
  • Why does MyISAM query perform well?
  • Transaction characteristics (ACID)
  • Isolation level
  • Common optimization steps for SQL slow queries?
  • Say optimistic locks, pessimistic locks (select for Update), and write the SQL implementation
  • TCP three-way handshake and four-way wave?
  • Which RPC frameworks have been used
  • How to implement database connection pool
  • Life cycle of Java Web filters

Three sides (combined side, about 1 hour)

  • To introduce myself
  • Is ConcurrentHashMap different in Java7 and Java8? Why is Java8 more concurrency efficient? When do you use HashMap and when do you use ConcurrentHashMap?
  • What is the mechanism of locking?
  • ThreadLocal? Application scenarios?
  • Database horizontal segmentation, vertical segmentation design ideas and segmentation sequence
  • How does Redis resolve key conflicts?
  • What is the difference between SOA and microservices?
  • What technical adjustments will be involved in the evolution of a stand-alone system to a distributed system? Please describe in detail from front load to back end
  • Design a seckill system?

Four sides (HR side)

1. What are your greatest strengths and weaknesses

2. What challenges have you met and how have you overcome them

3. What is your solution to the problem that technology cannot solve at work?

4. What are your hobbies?

5. What are your future career plans?

Headlines Java background 3 side

The headline on one side

1. Talk about the JVM runtime data repository

2. Tell me about the garbage collection algorithm you know

3. JVM memory model JMM

4. Difference between memory leakage and memory overflow

5. What is the difference between Select and EPool? What are the underlying data structures?

6. Mysql database default storage engine, what are the advantages

7. Optimize database methods, from SQL to cache to CPU to operating system, speak as much as you know

8. When do we divide tables and when do we divide databases

9. The difference between linkedList and arrayList applies to scenarios

10. How is array List expanded

11. What does the volatile keyword do? Java memory model?

12. Java Lock implementation, fair lock, unfair lock

Pessimistic lock and optimistic lock, application cases, how to implement mysql, Java implementation

Headline 2 face

  • Java Memory allocation Policy? How to allocate memory when multiple threads request it at the same time?
  • What data structures are used underneath Redis? What was done with Redis’ set?
  • What are the problems with Redis? Have you built a Redis cluster?
  • How to analyze slow Query logs for SQL/ index optimization?
  • MySQL > select * from ‘MySQL’; (B + tree)
  • How does the MySQL Hash index apply? What are some examples?

Headlines on three sides

  • How to ensure that the database is consistent with redis cache
  • What are Redis’ concurrency competition issues? How to solve this problem? Do you know the CAS scheme for Redis transactions?
  • How to ensure high concurrency and availability of Redis?
  • The master-slave replication principle of Redis, and the Sentry principle of Redis?
  • If you were to write a message queue, how would you architecture it? Tell me what you think.
  • How to implement primary/secondary synchronization in MySQL database?
  • How is the second kill module designed, how to pressure measurement, pressure resistance means?

Today’s headlines Java background research and development three

One side

  • Which are used under the Concurrent package?
  • Countdownlatch is implemented
  • Synchronized is different from lock
  • The difference between thread and runnable
  • AtomicInteger Implementation principle (CAS spin)
  • Java concurrency between sleep and Wait, notify and notifyAll
  • How to implement efficient synchronous linked lists
  • Synchronized, ReentrantLock, shared lock, read/write lock, etc.
  • Design patterns (factory pattern, singleton pattern (in several cases), adapter pattern, decorator pattern)
  • Maven dependency tree, Maven dependency passing, cyclic dependency

Second interview

  • What is the difference between synchronized and reentrantLock?
  • Introduce IOC and AOP of Spring, how to implement them respectively (classloader, dynamic proxy)
  • JVM memory layout and garbage collection principle and process talk, talk about CMS garbage collector garbage collection process, as well as CMS shortcomings
  • How does Redis handle inconsistencies caused by distributed server concurrency
  • The mechanism of OSGi
  • Spring bean loading mechanism, specific steps of bean generation, IOC injection
  • When Spring creates the applicationContext
  • Which event is the listener listening for?
  • What kind of lock is used? Is it possible to increase the segment?
  • Mysql index, b tree, why not balance binary tree, red black tree
  • How do I synchronize Zookeeper configurations

On three sides

  • Java thread pool ThreadPoolEcecutor parameter, basic parameter, usage scenario
  • MySQL ACID extends to isolation levels
  • Dubbo implementation principle, talk about the key points of RPC
  • GC pauses cause, how to reduce pauses?
  • How is the JVM tuned and how are its parameters tuned?
  • How to analyze JVM state with tools (visualVM looks at allocation of objects in the heap, references between objects, whether there are memory leaks, JStack looks at thread state, whether there are deadlocks, etc.)
  • Description consistent Hash algorithm (Redis)
  • How can distributed avalanche scenarios be avoided?
  • Let’s talk about message queues