Ali side


Briefly describe the most rewarding thing you did in school (technology-related)
Your project uses databases. Talk about your understanding of transactions
If you want to make a banking app, it is possible that more than one person will transfer money to one account at the same time. What problems will you encounter and how to solve them (lock)?


Talk about optimistic locks and pessimistic locks
What are you reading these days
Java basics (just ask == and equals)


Tell us what sort algorithms we can write now


Did you join a club or something at school
Given a file name, how to find this file in disk D, talk about ideas.
Can you come to Hangzhou? (I intend to write Beijing)
When will you be able to do the internship


It only took 20 minutes, and I felt like everything was simple.
However, the 11th evening interview, or today in the interview, is to cool 😥


Jingdong side


Tell me a little bit about yourself
What projects have you done
What specialized courses/techniques have you studied
Linked lists, advantages and disadvantages of arrays, application scenarios, complexity of finding elements
How is binary tree implemented


What locks are available in Java
What is the design idea of reentrant lock
Optimistic locks and pessimistic locks
Synchronized mechanism
Hashmap principle, which method is used to handle hash collisions (zippers)
What else do you know about handling hash collisions (open address detection)
How is open address detection implemented
If you delete an element from the hash table, and you add an element that conflicts with the original hash, where does that element go


Concurrent containers, Hashtable and ConcurrenthashMap
Java object headers
Know which sorting algorithms
How is quicksort implemented
How to implement heap sort
An algorithm problem: two ordered arrays, have the same elements, find out


Transaction characteristics (ACID)
Isolation level
Simple SQL statement (update)
Index mechanism, clustered index and non-clustered index
How to create an index
Database design (Orders, shopping carts, and items)


Understand the Java framework


Know which design patterns
Talk about adapter patterns, decorator patterns, proxy patterns
What books have you read recently
Do you have any questions for me



Jingdong’s chat lasted a full 40 minutes, asking too much




Jingdong 2 face


Introduce yourself
What books have you read?
The difference between String, StringBuilder and StringBuffer
How is string immutable implemented
Why is string made immutable
What are the commonly used collection frameworks
Introduce the Hashtable
Alternatives to Hashtable
What are the improvement strategies for exclusive locking
Design patterns know which ones. Just a quick introduction
Which databases have been used
Database index
A database can have several clustered indexes
Which engines support clustered indexes
The three major paradigm
So binary trees
How is quicksort implemented
A problem:
How do you quickly calculate the sum of 10 million random elements in a set?
How multithreading is used
One thread busy, multiple threads idle how to solve
TCP and UDP
Do you know the framework of Java? (I said I had not used Java before, and learned Python more, so the topic turned to Python)
Flask vs. Django (flask vs. Django)
How is ORM implemented
How does ORM optimize SQL
Compare Python with Java
What are the problems with multiple inheritance mechanisms? (After I answered the question, the interviewer said he couldn’t remember 😂😂.)
Any other questions for me


Two face more than 30 minutes, feel jingdong interviewers are very young ah, and the attitude is quite good, can not say the place will guide you. Finally, I asked the interviewer if he had any advice for me. He said that I was not very good either.

Gold-digging techniques: links to 👉 juejin.cn/post/1