Do java development for 7 years, 9 months this year to realize your dream? P7

Java tinker 2020-11-07 20:15:21
java development years months year


Working screw , Interview to build rocket . I think this is a headache for every programmer ! however , You have to go through an interview process , Especially when you can't figure out what the interviewer is asking , Lead to the interview did not know how to answer .
This paper is the work of 7 year Java Some of the more likely to be selected from the interview , I promise you've been asked ( Just so confident ), I hope it can help you find a job .



The following interview questions are just a small part of my frequently asked questions , In addition, I organize and collect 20 Interview questions of many companies in 1998 , As well as a variety of Java Core knowledge points can be shared for free , The bottom part is just a part of the map .
Friends in need can click on the portal to get Java Interview questions : 




One 、JVM A series of interview questions

1、 Partitions in the heap :Eden,survival (from+ to), Old age , Their characteristics .

answer :JVM It is divided into heap area and stack area , And the method area , The initialized object is put in the heap , References on the stack ,

class Class information constant pool (static Constant and static Variable ) Wait in the method area

new:① Method area : Mainly storage information , Constant pool (static Constant and static Variable ), Compiled code ( Bytecode ) Data such as

② Pile up : Initialized objects , Member variables ( That's not static The variable of ), All object instances and arrays are allocated on the heap

③ Stack : Stack structure is composed of stack frame , Call a method and press in a frame , Local variable table stored above frame , The stack of operands , Method exit information , The local variable table stores 8 Big foundation type plus an application type , So it's still an address pointer

④ Native Method Stack : Mainly for Native Method service

⑤ Program counter : Record the line number of current thread execution

2、GC Two judgment methods of :

3、SafePoint What is it?

4、GC Three collection methods of : Mark clear 、 Tag to sort out 、 Principle and characteristics of replication algorithm , Where to use them separately , If you want to optimize the collection method , What's the idea ?

5、Minor GC And Full GC When do they happen ?

6、JVM What are the areas of memory , What is the role of each zone ?

7、 How to judge whether an object is alive ?( perhaps GC The method of judging objects )

Two 、Redis A series of interview questions

1、Redis And memcached What are the advantages over ?

2、Redis Which data types are supported ?

3、Redis What are the data elimination strategies ?

4、 Why? Redis You need to put all the data in memory ?

5、Redis When will the cluster scheme cause the whole cluster to be unavailable ?

6、MySQL Are there in 2000w data ,redis The only known 20w The data of , How to ensure redis The data in is hot data ?

7、Redis and Redisson What does it matter ?


3、 ... and 、 Mysql A series of interview questions

1、Mysql What are the technical characteristics of ?

2、 stay Mysql in ENUM What is the usage of ?

3、 And Oracle comparison ,Mysql What are the advantages ?

4、 What string types of columns can be ?

5、 Please briefly describe Mysql in InnoDB Four supported transaction isolation level names , And the difference between levels ?

6、LIKE Statement % and _ What does that mean? ?

7、MyISAM Where will the forms be stored , And also provides its storage format ?

Four 、Netty A series of interview questions

1、BIO、NIO and AIO The difference between ?

answer :BIO: One connection, one thread , When the client has a connection request, the server will Need to start a thread to process . High thread overhead .

Pseudo asynchrony IO: Put the request connection into the thread pool , One to many , But threads are still a valuable resource .

NIO: One request, one thread , But the connection requests sent by the client are registered on the multiplexer , Multiplexing

The connection to the poller is I/O Start a thread to process when requested .

AIO: A valid request, a thread , Client's I/O All requests were made by OS First complete and then inform the server application to start the thread for processing ,BIO It's stream oriented ,NIO It's buffer oriented ;BIO The various streams of are blocked . and NIO It's non blocking ;BIO Of Stream Is one-way , and NIO Of channel It's two-way .

NIO Characteristics : Event driven model 、 Single thread processing multitasking 、 Non blocking I/O,I/O Reading and writing are no longer blocked , It's going back to 0、 be based on block Is more efficient than stream based transmission 、 More advanced IO function zero-copy、IO Multiplexing greatly improves Java Scalability and practicality of network applications . be based on Reactor Threading model .

stay Reactor In the pattern , The event distributor waits for an event or the state of an application or operation to occur , The event distributor will pass this event to the pre registered event handler or callback function , The latter does the actual reading and writing operations . If in Reactor To realize reading in : Register the read ready event and the corresponding event handler 、 The event distributor waits for events 、 The event came , Activate distributor , The dispatcher calls the handler corresponding to the event 、 The event handler completes the actual read operation , Processing read data , Register new events , And then return control .

2、TCP Sticky package / The reason and solution of unpacking ?

3、 Know which serialization protocols ?

4、 How to choose serialization protocol ?

5、Netty Zero copy implementation of ?

6、.Netty What is the performance of the high performance of ?

5、 ... and 、SQL Optimize a series of interview questions

1、Mysql What are the technical characteristics of ?

answer :Mysql Database software is a client or server system , These include : Supports multithreading of various client programs and libraries SQL The server 、 Different back ends 、 A wide range of application programming interfaces and management tools .

2、Heap What is a watch ?

3、Mysql What is the default port of the server ?

4、 And Oracle comparison ,Mysql What are the advantages ?

5、 distinguish CHAR_LENGTH and LENGTH?

6、Mysql What storage engine is used in ?

6、 ... and 、Duddo A series of interview questions

1、Dubbo in zookeeper Be a registry , If all the registry clusters hang up , Can publishers and subscribers still communicate ?

2、dubbo Service load balancing strategy ?

3、Dubbo How to solve this problem in terms of security mechanism

4、dubbo The difference between connecting a registry and a direct connection

5、dubbo Service cluster configuration ( Cluster fault tolerant mode )

6、dubbo Communication protocol dubbo Why do agreements require more consumers than providers :

7、dubbo Communication protocol dubbo Scope and scenario of application of the agreement

7、 ... and 、 Design pattern series interview questions

1、 Please list in JDK Several common design patterns in ?

answer : The singleton pattern (Singleton pattern) be used for Runtime,Calendar And some other classes . Factory mode (Factory pattern) Used for various immutable classes such as Boolean, image Boolean.valueOf, Observer mode (Observer pattern) Be used for Swing And a lot of event monitoring . Decorator design pattern (Decoratordesign pattern) Used for more than one Java IO Class .

2、 What is design pattern ? Have you ever used any design patterns in your code ?

3、Java What is singleton design pattern in ? Please use Java Write a thread safe singleton pattern

4、 stay Java in , What is observer design pattern (observer design pattern)?

5、 What are the main benefits of using the factory model ? Where to use ?

6、 Let's take one Java Realized decoration mode (decorator design pattern)? Does it work at the object level or the class level ?

7、 Give examples of situations where abstract classes are more likely to be used than interfaces ?



For the above interview questions , I summed up the Internet companies Java In the programmer interview , Most of the interview questions involved ( A detailed explanation of the answer is attached ). It's documented and PDF Format information , Free to share . Include Dubbo、Redis、Netty、Zookeeper、Spring Cloud、 Distributed 、 High concurrency and other architecture technology point core data ), Hope to help you review before the interview and find a job you like . meanwhile , It also saves you the time to study by searching for information online , You can also pay attention to me, and there will be more dry goods to share in the future ~



Speaking of this , Everyone must be ready to move , Because of the number of words in the article , You can't upload all the information , Friends who need information can click on the portal to get Java Interview questions : 


本文为[Java tinker]所创,转载请带上原文链接,感谢

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