Interview questions you should know

JAVA interview questions you should know I
often interview some candidates, and I have sorted out the questions I used for interviews. There are many questions that I have sorted out one after another, so I will select a part to ask each time. Answers will be published gradually in subsequent articles.


Basic topic
Java thread status Difference between
process and thread, how to communicate between processes, how to communicate between threads
What is the data structure of HashMap? how to achieve. The difference between HashTable and ConcurrentHashMap The difference between
Cookie and Session What is the use of
index ? How to build an index?
How is ArrayList implemented, the difference between ArrayList and LinkedList? How to achieve expansion of ArrayList.
The equals method implements object
-oriented
thread state, what is the difference between BLOCKED and WAITING,
how JVM loads bytecode files
JVM GC, GC algorithm.
Under what circumstances will Full GC occur and under what circumstances will Yong GC occur.
JVM memory model
Java runtime data area
Transaction implementation principle


Technical depth


Have you read the JDK source code and what is the implementation principle of the class you have read?
HTTP protocol
TCP protocol
Consistent Hash algorithm
How JVM loads bytecode files How
class loader unloads bytecode
The difference between IO and NIO, the advantages of NIO
The implementation principle of Java thread pool, the role of parameters such as keepAliveTime.
Implementation principle of HTTP connection pool Implementation principle of
database connection pool Implementation principle of
database


Technical framework


Which open source framework source codes have you seen?
Why use Redis? What are the advantages and disadvantages of Redis? How does Redis scale up?
How does Netty use the thread pool and why it is used
Why use Spring? What are the advantages and disadvantages of Spring?
Spring's IOC container initialization process Spring's IOC container implementation principle, why can I find the Bean Spring AOP implementation principle
through byName and ByType? Message middleware How is it implemented and what are the technical difficulties System architecture How to build a high-availability system Which design patterns can increase the scalability of the system Introduce design patterns, such as template pattern, command pattern, strategy pattern, adapter pattern, bridge pattern, decoration pattern, Observer pattern, state pattern, visitor pattern. Abstract ability, how to improve R&D efficiency. What is high cohesion and low coupling? Please give an example of how to implement it . When to use interface and when to use message In what scenarios should the system be combined The difference between systems and modules, and in what scenarios are distributed systems used






















Distributed transaction, two-phase commit.
How to implement distributed locks
How to implement distributed sessions
How to ensure message consistency
Load balancing
Forward proxy (client proxy) and reverse proxy (server proxy)
CDN implementation principle
How to improve the QPS and throughput of the system


Practical capability


Is there any Dealing with online issues? There is a memory leak, the CPU utilization is high, and how to deal with the application when it is not responding.
Have you encountered any technical problems during development? How to solve
it If there are billions of whitelists, high concurrent queries are required during the day, and updates are required at night, how to design this function.
How Sina Weibo pushes Weibo to subscribers
How Google returns search results to users within a second.
How to implement the booking system of the 12306 website and how to ensure that the tickets will not be oversold.
How to implement a seckill system to ensure that only a few users can buy a certain product.


Soft skills


How to learn a new technology, such as how to learn Java, what
to focus on learning What new technologies to focus on How to handle when there are too many and very complicated
work tasks How to deal with
project delays How to deal
with different design ideas from colleagues
How to ensure development Quality What is
career planning? What are the short-term and long-term goals? What is the
team 's plan?
Can you describe where you have grown from work to now?