preface

As a Java programmer, you’re stuck in business development, pounding away at code, from system development to Bug fixing, and you feel like you can do anything. However, once in a while at a party, you hear that your classmate who started out with you already has an annual salary of 500,000 yuan, while you are strapped for cash. So you want to look at new opportunities, find a new platform, and thrive.

But when that smiling interviewer asks you a Java question you know all too well, you just feel deja vu and can’t answer it. How HashMap works, for example, or how volatile is used.

At this time, you may doubt your ability and hate why you didn’t study hard enough.

This new version of the document has been uploaded on Github for a week and has received 30K+ STAR Java core interview magic skills (this parameter, the quality of how high I need to say it) is very comprehensive. Includes Java foundation, Java collections, JavaWeb, Java exceptions, OOP, IO and NIO, reflection, annotations, multithreading, JVM, MySQL, MongoDB, Spring family bucket, computer network, distributed architecture, Redis, Linux, Git, front-end, algorithms and data structures, M YBatis, RocketMQ, Netty, Dubbo, Zookeeper, distributed cache, data structure and other content is very rich, has helped many people to win the offer of first-tier Internet companies. Let me share it with you.

JavaOOP

  • What is the B/S architecture? What is the C/S architecture
  • What are the development platforms for Java?
  • What is the JDK? What is the JRE?
  • What are the features of the Java language
  • The difference between object-oriented and procedural
  • What is a data structure?
  • What are Java data structures?
  • OOP is what?
  • Class and object relationships?
  • There are several data types in Java

 

Due to the space limitation, the detailed information of the PDF document is too comprehensive, the details are too much, so only part of the knowledge point screenshots out of the rough introduction, each small node there are more detailed content!

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Java collections/generics

  • Difference between ArrayList and linkedList
  • Difference between HashMap and HashTable
  • Collection package structure, different from Collections
  • Common characteristics of generics (to be added)
  • Tell me the difference between List,Set and Map
  • How is an Array different from an ArrayList?
  • What are the features of Map
  • The collection is housed in the java.util package and has several main interfaces
  • What is the List interface
  • So ArrayList

 

Due to the details of the document is too much so only edited part of the knowledge of the chapter rough introduction, each chapter of the small nodes there are more detailed content! The following is part of the chapter table of contents. Due to space limitation, the detailed explanation in the table of contents cannot be listed one by one. At the end of the article, all the detailed knowledge in the following chapters can be obtained.

Java exception

  • What are the two types of exceptions in Java?
  • How many mechanisms are there for handling exceptions?
  • How do I customize an exception
  • Try catch fifinally, try has a return, finally is executed?
  • Excption with Error package structure
  • Thow is different from Thorws
  • What is the difference between Error and Exception?
  • What is the difference between Error and exception

 

IO and NIO in Java

  • IO streams in Java?
  • Java IO vs. NIO
  • What are the common I/O classes
  • The difference between a byte stream and a character stream
  • Blocking IO model
  • Non-blocking IO model
  • Multiplexing IO model
  • Signal driven IO model
  • Asynchronous IO model
  • JAVA NIO

 

Java reflection

  • What other methods can you use to create objects besides using new?
  • Is it more efficient to create objects with Java reflection or with New?
  • The role of Java reflection
  • Where does reflection come in?
  • Reflection is implemented by:
  • Classes that implement Java reflection
  • Pros and cons of reflection:
  • The Java reflection API
  • Reflection usage steps (get Class objects, call object methods)
  • There are several ways to get a Class object
  • Use reflection to dynamically create object instances

 

Java serialization

  • What is Java serialization and how is it implemented?
  • Save (persist) objects and their state to memory or disk
  • Serialized objects are held as byte arrays – static members are not saved
  • Serialized user remote object transfer
  • Serializable implements serialization
  • WriteObject and readObject customize serialization policies
  • Serialization ID
  • Serialization does not hold static variables
  • The Transient keyword prevents the variable from being serialized to a file
  • Serialization (deep Clone 1 implementation)

 

Multithreading & Concurrency

JAVA Concurrent Knowledge base

  • There are several ways to implement multithreading in Java
  • Thread class inheritance
  • Implement the Runnable interface.
  • ExecutorService, Callable, and Future have return value threads
  • Thread pool-based approach
  • Four thread pools
  • How do I stop a running thread
  • What’s the difference between notify() and notifyAll()?
  • What is the difference between sleep() and wait()?
  • What is volatile? Can order be guaranteed?

 

JVM

  • Is there a memory leak in Java? Please describe it briefly.
  • In 64-bit JVMS, is the length of an int the majority?
  • What are the differences between Serial and Parallel GC?
  • For 32-bit and 64-bit JVMS, is the length of a variable of type int the majority?
  • Difference between WeakReference and SoftReference in Java?
  • What does the JVM option -xx :+UseCompressedOops do? Why use it
  • How do I determine whether the JVM is 32-bit or 64-bit using a Java program?
  • What is the maximum heap memory for 32-bit and 64-bit JVMS?
  • What are the differences between the JRE, JDK, JVM, and JIT?
  • Explain Java heap space and GC?

 

Mysql

  • Database storage engine
  • InnoDB (B+ tree)
  • TokuDB (Fractal Tree- Nodes with data)
  • Memory
  • What are the database engines
  • Differences between InnoDB and MyISAM
  • The index
  • Common indexing principles are
  • What are the three paradigms of databases
  • 1st NF – columns are non-separable

 

Redis

  • What is Redis?
  • How is Redis different from other key-value stores?
  • Redis data type?
  • What are the benefits of using Redis?
  • What advantages does Redis have over Memcached?
  • What are the differences between Memcache and Redis?
  • Is Redis single process single thread?
  • What is the maximum size of intelligent storage for a string?
  • Redis persistence mechanism
  • Cache avalanche, cache penetration, cache warming, cache update, cache degradation and other issues

 

Memcached

  • What is Memcached and what does it do?
  • What are the application scenarios of memcached service in enterprise cluster architectures?
  • How to implement distributed cluster of Memcached service?
  • What are the features of the Memcached service and how it works?
  • How does Memcached memory management work?
  • How does memcached work?
  • What is memcached’s biggest advantage?
  • Memcached and MySQL query
  • How does memcached compare to a server’s local cache, such as PHP APC, Mmap files, etc.?
  • What is the cache mechanism for memcached?
  • How does memcached implement redundancy?

 

MongoDB

  • What is mongodb?
  • What are the features of mongodb?
  • What do you mean by NoSQL database? What is the difference between NoSQL and RDBMS directly? Why use and not use NoSQL databases? What are the advantages of NoSQL databases?
  • What are the types of NoSQL databases?
  • What are the basic differences between MySQL and MongoDB?
  • How do you compare MongoDB, CouchDB, and CouchBase?
  • What makes MongoDB the best NoSQL database?
  • Does journal playback have problems with incomplete entries (such as one that happens to fail midway)?
  • What is the role of profilers in MongoDB?
  • What is a namespace?

 

Spring

  • What are the main features of the different versions of the Spring Framework?
  • What is the Spring Framework?
  • List the advantages of the Spring Framework.
  • What are the different features of the Spring Framework?
  • How many modules are there in the Spring Framework, and what are they?
  • What is a Spring configuration file?
  • What are the different components of a Spring application?
  • What are some ways to use Spring?
  • What is the Spring IOC container?
  • What is dependency injection?

 

Spring Boot

  • What is Spring Boot?
  • Why SpringBoot
  • What are the advantages of Spring Boot?
  • What are the core annotations for Spring Boot? Which notes are it mainly composed of?
  • How many ways to run Spring Boot
  • How do you understand the Starters in Spring Boot?
  • How do I run some specific code when Spring Boot starts?
  • Does Spring Boot need a separate container to run?
  • What is a monitor in Spring Boot?
  • How do I implement exception handling using Spring Boot?

 

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Spring Cloud

  • What is Spring Cloud?
  • What are the advantages of using Spring Cloud?
  • What do I mean by service registration and discovery? How is Spring Cloud implemented?
  • What does load balancing mean?
  • What is Hystrix? How does it achieve fault tolerance?
  • What is Hystrix circuit breaker? Do we need it?
  • What is Netflix Feign? What are its advantages?
  • What is Spring Cloud Bus? Do we need it?
  • What are microservices
  • What is a service circuit breaker? What is service degradation

 

RabbitMQ

  • What is the rabbitmq
  • Why use RabbitMQ
  • Rabbitmq scenarios
  • How do I ensure that messages are sent to RabbitMQ correctly? How do I ensure that message recipients consume messages?
  • How can I avoid double-delivery or double-consumption of messages?
  • What transport is the message based on?
  • How are messages distributed?
  • How are messages routed?
  • How do I ensure that messages are not lost?
  • What are the benefits of using RabbitMQ?

 

Dubbo

  • Why Dubbo?
  • What are the layers of Dubbo’s overall architectural design?
  • What communication framework is used by default, and what other options are there?
  • Is the service invocation blocking?
  • What registry is commonly used? Is there any other option?
  • What serialization framework is used by default, and what else do you know?
  • What is the principle that service providers can achieve invalidation?
  • How does the launch of the service not affect the old version?
  • How to solve the problem of long service invocation chains?
  • What are the core configurations?

 

MyBatis

  • What is Mybatis?
  • The advantages of Mybaits
  • Disadvantages of MyBatis framework
  • MyBatis framework for applications
  • What are the differences between MyBatis and Hibernate?
  • What is the difference between {} and ${}?
  • What if the attribute name in the entity class is different from the field name in the table?
  • How to write fuzzy query like statement?
  • Usually an Xml mapping file will write a Dao interface corresponding to it. What is the working principle of this Dao interface? Can methods in the Dao interface be overloaded if their parameters are different?
  • How do I get automatically generated (primary) key values?

 

ZooKeeper

  • What is a Zookeeper?
  • How does Zookeeper ensure distributed consistency?
  • What does ZooKeeper offer?
  • Zookeeper file system
  • ZAB agreement?
  • Four types of data nodes zNodes
  • Zookeeper Watcher mechanism – Data change notification
  • The client registers the Watcher implementation
  • The server handles the Watcher implementation
  • The client calls back Watcher

 

The data structure

  • The stack (stack)
  • Queue
  • Linked list
  • Hash Table
  • Sort binary trees
  • The prefix tree
  • Red and black tree
  • B-TREE
  • The bitmap

 

Elasticsearch

  • How many shards are there, how many are there, and how many tuning methods are there?
  • What is the inverted index of ElasticSearch
  • Select * from elasticSearch; select * from elasticSearch
  • How does ElasticSearch implement master voting
  • Describe the process of indexing documents for Elasticsearch in detail
  • How does Elasticsearch search work?
  • How to optimize the Settings for Linux when Elasticsearch is deployed
  • What is the internal structure of Lucence?
  • How does Elasticsearch implement Master voting?
  • What if 10 of the 20 Elasticsearch nodes select one master and the other 10 select another master?

 

Kafka

  • What is Kafka
  • Partition data file (offset, MessageSize, data)
  • Data file segment (sequential read and write, segment command, binary search)
  • Load balancing (partitions are evenly distributed among different brokers)
  • Batch send
  • Compression (GZIP or Snappy)
  • Consumer design
  • Consumer Group
  • How do I get a list of topic topics
  • What is the producer and consumer command line?

 

Micro service

  • What are the advantages of microservices architecture?
  • What are the features of microservices?
  • What is the best time to design a microservice?
  • How does the microservices architecture work?
  • What are the advantages and disadvantages of microservices architecture?
  • What are the differences between monolithic, SOA and microservice architectures?
  • What challenges do you face when using the microservices architecture?
  • What are the key differences between SOA and microservice architectures?
  • What are the features of microservices?

 

Linux

  • What’s the notation for an absolute path? What are the current and upper directories represented by? What is the home directory? What command is used to switch directories?
  • How do I view the current process? How do I exit? How do I view the current path?
  • How do I clear the screen? How do I exit the current command? How to perform sleep? How to check when
  • What function does the Ls command perform? What parameters can be taken and what is the difference?
  • See what commands the file has
  • List a few common Linux commands
  • How do you check your logs?
  • Commands to create soft links (shortcuts) and hard links
  • What command does directory creation use? What command is used to create a file? What command is used to copy files?
  • What commands can be used to view file contents?

 

Interview, difficult or not difficult? Is the end result good or bad? It depends on the interviewer’s background (aura + skill), mentality and cognition, and communication skills. And some mainstream large Internet companies interview (Alibaba, JINGdong, Meituan, Didi) is to show your ability in the interview, so as to get the interviewer’s appreciation and affirmation.

And programmers need to go through layers of interviews. As the saying goes, sharpness is not the mistake of cutting wood, do a good job of preparation before the interview can help you better deal with the interviewer’s questions and the interview in the emergency situation.

Due to the space limitation, the detailed information of the PDF document is too comprehensive, the details are too much, so only part of the knowledge point screenshots out of the rough introduction, each small node there are more detailed content!

Need this “Java interview notes” complete version of the friends please forward + follow the public number below to get free