Preface

I have been sharing technical articles with you all the time. I believe you have already learned the techniques you should learn. It is time to test your own technical depth and breadth, that is, job-hopping interviews; 4. During the peak period of salary increase during the interview, I wonder if everyone is ready?

Today, I prepared a wave of benefits for everyone, that is, the latest 897 java interview questions and answers shared by Ali P7 architects open source in 2021. I hope to help you, and hope to be liked by everyone! ! ! Repost a lot to benefit more people! !

Click here to receive it~

A total of 32 interview questions are included, and I will introduce them one by one below.

7 message queue ActiveMQ interview questions

1. What is ActiveMQ?

activeMQ is an open source, message-oriented (MOM) middleware that implements the JMS1.1 specification, and provides efficient, scalable, stable and secure enterprise-level message communication for applications;
2. ActiveMQ server is down What about the machine?

3. What should I do if I lose a message?
4. Persistent messages are very slow.
5. Uneven consumption of news.
6. Dead letter queue.
7. Is the message retransmission interval and retransmission times in ActiveMQ?

9 classic distributed caching Redis + Memcached interview questions

1 What are the advantages of Redis over memcached?
2 Which data types does Redis support?
3 What should the Redis cluster solution do? What are the options?
4 What algorithm does Redis use for recycling?
5 Why do Redis partitions?
6 How about the memory usage of Redis?
7 What are the features and working principle of Memcached service?
8 How to realize session shared storage in a cluster?
9 The difference between memcached and redis?

10 Netty Interview Questions for Advanced Java

1. What is the difference between BIO, NIO and AIO?
2. What is the composition of NIO?
3. What are the characteristics of Netty?
4. Netty's threading model?
5. The reasons and solutions for TCP sticking/unpacking?
6. What kind of serialization protocols do you know?
7. How to choose serialization protocol?
8. What is Netty's zero-copy implementation?
9. What are the high performance of Netty?
10. NIOEventLoopGroup source code?

10 essential design pattern interview questions for Java interviews

1. Please list several commonly used design patterns in JDK?
2. What is a design pattern? Have you used any design patterns in your code?
3. What is the singleton design pattern in Java? Please write a thread-safe singleton pattern
in Java. 4. What is the observer design pattern in Java?
5. What are the main benefits of using the factory model? Where is it used?
6. Give a decorator design pattern implemented in Java? Does it act on the object level or the class level?
7. In Java, why is it not allowed to access non-static variables from static methods?
8. To design an ATM machine, please tell us your design ideas?
9. In Java, when do you use overloading and when do you use rewriting?
10. Give examples to illustrate when you would prefer to use abstract classes instead of interfaces?

10 classic Java List interview questions

1. What lists do you know?
2. What is the difference between List and Vector?
3. Is List ordered?
4. What is the difference between ArrayList and LinkedList? What scenarios are they used in?
5. What is the underlying data structure of ArrayList and LinkedList?
6. What is the default size of ArrayList and how is it expanded?
7. Is List thread safe? What if you want to be thread safe?
8. How to sort List?
9. Can the List after the Arrays.asList method be expanded?
10. How to convert between List and Array?

10 Java Classic Main Method Interview Questions

1. What is the main method for?
2. How to run a class without the main method?
3. How does the main method pass parameters? What type of parameters are passed? Can the parameter type be changed?
4. Why is the main method static? Can it be changed to non-static?
5. Can the main method be overloaded?
6. Can the main method be overridden?
7. What is the return type of the main method? Can it be changed?
8. What modifies the scope of the main method? Can it be changed?
9. Can the main method be synchronized?
10. Can the main method be terminated?

10 classic Java String interview questions

1. Is String a basic data type?
2. Is String variable?
3. How to compare two strings with the same value, how to compare whether two strings are the same object?
4. Can String be used in switch?
5. String str = new String("abc"); Several objects have been created, why?
6. What is the difference between String, StringBuffer and StringBuilder?
7. Which characters are removed by the String.trim() method?
8. Can String be inherited by subclasses?
9. Can the java.lang.String class be customized and used?
10. How to convert between String and byte[]?

15 classic Tomcat interview questions

1. What is the default port of Tomcat and how to modify it?
2. What kinds of connector operating modes (optimization) does tomcat have?
3. How many deployment methods does Tomcat have?
4. How does the tomcat container create an instance of the servlet class? What principle was used?
5. How to optimize Tomcat?
6. Memory tuning
7. Garbage collection strategy tuning
8. Shared session processing
9. Professional analysis tools are
10. About the number of Tomcat sessions
11. Monitoring Tomcat's memory usage
12. Printing class loading and object status Recycling situation
13. Tomcat The complete process of a request
14. Tomcat working mode?
15. Add JMS remote monitoring

15 Java multithreaded interview questions frequently asked in interviews

1) There are three threads, T1, T2, and T3. How do you ensure that T2 is executed after T1 is executed, and T3 is executed after T2 is executed?
2) What are the advantages of the Lock interface over the synchronized block in Java? You need to implement an efficient cache that allows multiple users to read but only one user to write to maintain its integrity. How would you implement it?
3) The difference between wait and sleep methods in java?
4) Implement blocking queue in Java.
5) Write code in Java to solve the producer-consumer problem.
6) Using Java to program a program that will cause a deadlock, how would you solve it?
7) What are atomic operations, and what are atomic operations in Java?
8) What is the key role of volatile in Java? How to use it? How is it different from the synchronized method in Java?
9) What are race conditions? How do you discover and resolve competition?
10) How will you use threaddump? How will you analyze Thread dump?
11) Why do we execute the run() method when we call the start() method, and why can’t we call the run() method directly?
12) How do you wake up a blocked thread in Java?
13) What is the difference between CycliBarriar and CountdownLatch in Java?
14) What is an immutable object, and how does it help to write concurrent applications?
15) What are the common problems you encounter in a multithreaded environment? How did you solve it?

17 message queue Kafka interview questions

1. What is the design of Kafka?
2. What are the three definitions of data transmission?
3. What are the two conditions for Kafka to judge whether a node is still alive?
4. Does the producer send data directly to the leader (master node) of the broker?
5. Can Kafa consumer consume messages from designated partitions?
6. Does Kafka message use Pull mode or Push mode?
7. What is the message format of Kafka stored on the hard disk?
8. Kafka efficient file storage design features:
9. There are three key differences between Kafka and traditional messaging systems
10. How to place partitions in different brokers when Kafka creates Topic
11. In which directory will Kafka create new partitions
12 How to save .partition data to the hard disk
13.kafka's ack mechanism
14. How Kafka consumers consume data
15. Consumer load balancing strategy
16. Data orderly
17. Kafaka data grouping strategy when producing data

18 very awesome Nginx interview questions

1. Please explain what is Nginx?
2. Please enumerate some features of Nginx.
3. Please list the differences between Nginx and Apache.
4. Please explain how Nginx processes HTTP requests.
5. In Nginx, how to use undefined server name to prevent processing requests?
6. What are the advantages of using "reverse proxy server"?
7. Please enumerate the best uses of Nginx server.
8. Please explain what are the Master and Worker processes on the Nginx server?
9. Please explain how you open Nginx through a port other than 80?
10. Please explain whether it is possible to replace Nginx errors with 502 errors and 503?
11 、In Nginx, explain how to keep the double slash in the URL?
12.
Please explain what is the function of ngx_http_upstream_module? 13. Please explain what is the C10K problem?
14. Please state what is the function of the stub_status and sub_filter instructions?
15. Explanation Does Nginx support compressing requests to the upstream?
16. Explain how to get the current time in Nginx?
17. Explain the purpose of -s with Nginx server?
18. Explain how to add modules on Nginx server?

20 top Spring Boot interview questions