Will interviews be more difficult in 2020? Java must have 209 real questions, this list will help you easily enter Ali

During the interview, if you are still chattering about incomprehensible, or if you are not answering the questions asked by the interviewer, you have basically given you the Pass in the interviewer’s heart. In order not to make the interviewer feel too frustrated, after all, It's not easy to come to find a job from a long distance, but I don't have the desire to talk anymore in my heart. Today, I will share some technical module analysis that is often asked in interviews. I hope this interview list will be helpful to friends who are looking for a job next year!

Introduction to Interview Questions Module

Having said that, let’s enter the topic of our article below. Our interview question contains nineteen modules: Java basics, containers, multithreading, reflection, object copy, Java Web modules, exceptions, networks, design patterns , Spring/Spring MVC, Spring Boot/Spring Cloud, Hibernate, Mybatis, RabbitMQ, Kafka, Zookeeper, MySql, Redis, JVM.

Specific interview questions

Let's take a look at the 208 interview questions, the specific content. (Due to the length of the space, in order not to affect everyone's reading effect, the article does not give an answer. I am here to share it in the form of a file for free, and programmers who need to borrow can click here to get it for free!! )

 

One, Java basics

 

1. What is the difference between JDK and JRE?
2. What is the difference between == and equals?
3. If the hashCode() of two objects is the same, equals() must also be true, right?
4. What is the role of final in java?
5. How much is Math.round(-1.5) in java?
6. Is String a basic data type?
7. What are the classes for manipulating strings in java? What is the difference between them?
8. Is String str="i" the same as String str=new String("i")?
9. How to reverse the string?
10. What are the common methods of the String class?
11. Do abstract classes have to have abstract methods?
12. What is the difference between a normal class and an abstract class?
13. Can abstract classes use final modification?
14. What is the difference between an interface and an abstract class?
15. How many types of IO streams are in java?
16. What is the difference between BIO, NIO and AIO?
17. What are the common methods of Files?

Second, the container

 

1. What are the java containers?
2. What is the difference between Collection and Collections?
3. What is the difference between List, Set and Map?
4. What is the difference between HashMap and Hashtable?
5. How to decide whether to use HashMap or TreeMap?
6. Tell me about the implementation principle of HashMap?
7. Tell me about the implementation principle of HashSet?
8. What is the difference between ArrayList and LinkedList?
9. How to realize the conversion between array and List?
10. What is the difference between ArrayList and Vector?
11. What is the difference between Array and ArrayList?
12. What is the difference between poll() and remove() in Queue?
13. Which collection classes are thread safe?
14. What is Iterator?
15. How to use Iterator? What are the characteristics?
16. What is the difference between Iterator and ListIterator?
17. How to ensure that a collection cannot be modified?

Three, multi-threaded

 

1. What is the difference between parallel and concurrency?
2. The difference between thread and process?
3. What is a daemon thread?
4. What are the ways to create threads?
5. What is the difference between runnable and callable?
6. What are the statuses of threads?
7. What is the difference between sleep() and wait()?
8. What is the difference between notify() and notifyAll()?
9. What is the difference between thread run() and start()?
10. What are the ways to create a thread pool?
11. What are the statuses of the thread pool?
12. What is the difference between the submit() and execute() methods in the thread pool?
13. How to ensure the safe operation of multiple threads in a java program?
14. What is the upgrade principle of multi-threaded locks?
15. What is a deadlock?
16. How to prevent deadlock?
17. What is ThreadLocal? What are the usage scenarios?
18. Talk about the underlying implementation principle of synchronized?
19. What is the difference between synchronized and volatile?
20. What is the difference between synchronized and Lock?
21. What is the difference between synchronized and ReentrantLock?
22. Tell me about the principle of atomic?

Four, reflection

 

1. What is reflection?
2. What is java serialization? Under what circumstances need serialization?
3. What is a dynamic proxy? What are the applications?
4. How to implement dynamic proxy?

Five, object copy

 

1. Why use cloning?
2. How to implement object cloning?
3. What is the difference between deep copy and shallow copy?

Six, Java Web

 

1. What is the difference between jsp and servlet?
2. What are the built-in objects of jsp? What are the roles?
3. Tell me about the 4 scopes of jsp?
4. What is the difference between session and cookie?
5. Tell me about the working principle of session?
6. Can the session be used if the client prohibits cookies?
7. What is the difference between spring mvc and struts?
8. How to avoid sql injection?
9. What is an XSS attack and how to avoid it?
10. What is a CSRF attack and how to avoid it?

Seven, abnormal

 

1. What is the difference between throw and throws?
2. What is the difference between final, finally, finalize?
3. Which part of try-catch-finally can be omitted?
4. In try-catch-finally, if the catch is returned, will finally be executed?
5. What are the common exception classes?

8. Network

 

1. What do the http response codes 301 and 302 represent? What's the difference?
2. The difference between forward and redirect?
3. Briefly describe the difference between tcp and udp?
4. Why does tcp need to shake hands for three times, can't it work twice? why?
5. Talk about how tcp sticky packets are produced?
6. What are the seven-layer models of OSI?
7. What is the difference between get and post request?
8. How to achieve cross-domain?
9. Tell me about the principle of JSONP implementation?

Nine, design patterns

 

1. Tell me about the design patterns you are familiar with?

• What is the difference between a simple factory and an abstract factory?

十、Spring/Spring MVC

 

1. Why use spring?
2. Explain what is aop?
3. Explain what is ioc?
4. What are the main modules of spring?
5. What are the common injection methods for spring?
6. Are beans in spring thread-safe?
7. What kind of scope does spring support for beans?
8. What are the ways to automatically assemble beans in spring?
9. What are the spring transaction implementation methods?
10. Talk about spring's transaction isolation?
11. Talk about the running process of spring mvc?
12. What are the components of spring mvc?
13. What is the purpose of @RequestMapping?
14. What is the role of @Autowired?

十一、Spring Boot/Spring Cloud

 

1. What is spring boot?
2. Why use spring boot?
3. What is the spring boot core configuration file?
4. What types of spring boot configuration files are there? What is the difference between them?
5. What are the ways to achieve hot deployment with spring boot?
6. What is the difference between jpa and hibernate?
7. What is spring cloud?
8. What is the function of spring cloud circuit breaker?
9. What are the core components of spring cloud?

Twelve, Hibernate

 

1. Why use hibernate?
2. What is the ORM framework?
3. How to view the printed sql statement in the console in hibernate?
4. How many query methods does hibernate have?
5. Can hibernate entity classes be defined as final?
6. What is the difference between using Integer and int for mapping in hibernate?
7. How does hibernate work?
8. What is the difference between get() and load()?
9. Talk about the caching mechanism of hibernate?
10. What are the statuses of hibernate objects?
11. What is the difference between getCurrentSession and openSession in hibernate?
12. Do hibernate entity classes have to have parameterless constructors? why?

13. Mybatis

 

1. What is the difference between #{} and ${} in mybatis?
2. How many paging methods does mybatis have?
3. Is RowBounds querying all results at once? why?
4. What is the difference between mybatis logical paging and physical paging?
5. Does mybatis support lazy loading? What is the principle of lazy loading?
6. Tell me about the first level cache and the second level cache of mybatis?
7. What are the differences between mybatis and hibernate?
8. What executors does mybatis have?
9. What is the realization principle of mybatis paging plug-in?
10. How to write a custom plug-in for mybatis?

14. RabbitMQ

 

1. What are the usage scenarios of rabbitmq?
2. What are the important roles of rabbitmq?
3. What are the important components of rabbitmq?
4. What is the role of vhost in rabbitmq?
5. How are rabbitmq's messages sent?
6. How does rabbitmq guarantee the stability of the message?
7. How does rabbitmq avoid message loss?
8. What are the conditions to ensure the success of message persistence?
9. What are the disadvantages of rabbitmq persistence?
10. How many types of broadcasts does rabbitmq have?
11. How does rabbitmq implement a delayed message queue?
12. What is the use of rabbitmq cluster?
13. What are the types of rabbitmq nodes?
14. What issues should be paid attention to when building a rabbitmq cluster?
15. Is each node of rabbitmq a complete copy of other nodes? why?
16. What happens if the only disk node in the rabbitmq cluster crashes?
17. Does rabbitmq have any requirements on the stopping order of cluster nodes?

15. Kafka

 

1. Can Kafka be used separately from zookeeper? why?
2. How many data retention strategies does Kafka have?
3. Kafka has set up 7 days and 10G to clear data at the same time. By the fifth day, the message reached 10G. What will Kafka do at this time?
4. What can cause Kafka to run slower?
5. What should I pay attention to when using Kafka cluster?

16. Zookeeper

 

1. What is zookeeper?
2. What are the functions of zookeeper?
3. How many deployment modes does zookeeper have?
4. How does zookeeper ensure the synchronization of the master and slave nodes?
5. Why is there a master node in the cluster?
6. There are 3 servers in the cluster, and one of the nodes is down. Can zookeeper still be used at this time?
7. Tell me about the notification mechanism of zookeeper?

Seventeen, MySql

 

1. What are the three paradigms of the database?
2. There are a total of 7 pieces of data in an auto-increment table, the last 2 pieces of data are deleted, the mysql database is restarted, and another piece of data is inserted. What is the id at this time?
3. How to get the current database version?
4. What is ACID?
5. What is the difference between char and varchar?
6. What is the difference between float and double?
7. What is the difference between inner connection, left connection, and right connection of mysql?
8. How is the mysql index implemented?
9. How to verify whether the mysql index meets the requirements?
10. Talk about the transaction isolation of the database?
11. Tell me about the engines commonly used in mysql?
12. Talk about the row lock and table lock of mysql?
13. Talk about optimistic locking and pessimistic locking?
14. What are the methods for mysql troubleshooting?
15. How to optimize the performance of mysql?

18. Redis

 

1. What is redis? What are the usage scenarios?
2. What are the functions of redis?
3. What is the difference between redis and memecache?
4. Why is redis single-threaded?
5. What is cache penetration? How to deal with it?
6. What data types does redis support?
7. What are the java clients supported by redis?
8. What is the difference between jedis and redisson?
9. How to ensure the consistency of cache and database data?
10. How many ways are redis persistence?
11. How does redis implement distributed locks?
12. What are the shortcomings of redis distributed locks?
13. How does redis optimize memory?
14. What are the redis elimination strategies?
15. What are the common performance problems of redis? How to solve it?

Nineteen, JVM

 

1. Talk about the main components of jvm? And its role?
2. Talk about the jvm runtime data area?
3. Tell me about the difference between stacks?
4. What are queues and stacks? What's the difference?
5. What is the parent delegation model?
6. Talk about the execution process of class loading?
7. How to judge whether the object can be recycled?
8. What are the reference types in java?
9. Tell me about what garbage collection algorithms does jvm have?
10. What garbage collectors does jvm have?
11. Tell me more about the CMS garbage collector?
12. What are the new-generation garbage collectors and the old-generation garbage collectors? What's the difference?
13. Briefly describe how the generational garbage collector works?
14. Talk about jvm tuning tools?
15. What are the commonly used jvm tuning parameters?

to sum up

The interview experience is just to provide you with some temporary coping skills. The real ability still depends on the usual learning and accumulation. Only when you learn more and master the technology thoroughly, will you be in danger and not be surprised during the interview. Although it is sometimes feasible to hold the Buddha's feet temporarily, there are also times when you can't hold it.

Interview questions, click here to get them for free! !