CMB network interview questions, test centers, knowledge summary (Java Kong)

java foundation

Needless to say, certainly is the basis for the whole test of many, especially the CMB

• OOP features / java language features: encapsulation, inheritance, polymorphism
• Polymorphism specific performance: polymorphic usage, how to call the parent class method (Super), and heavy rewritten (rewrite rules parent class method, constructor can override ..)
• The difference between abstract classes and interfaces, and pass a reference value is passed, java value transfer only: class, an abstract class, an interface
• Generics
• Reflection: the significance of class Class
• StringBuffer, StringBuilder, String difference: String common method
• static keyword in the memory area
• What are commonly used java package
• final keyword
• Create a new object's methods
• How java cache (, memcache nothing to do with redis)

container

simple

• Hierarchy set of classes, briefly
• The difference between equals (), hashcode (), the rewriting Notes
• TreeMap understand it
• HashMap, HashTable, ConcurrentHashMap: difference, hashMap implementation principle, put way to do what the underlying source code, custom classes into the requirements of the hashmap (override equals and hashcode)
• LinkedList and ArrayList difference

Thread

The difficulty is asked handwritten threaded code, and that even if their luck; otherwise fairly simple thread

• Threads and processes
• Thread define the difference between methods that are
• Thread state transition diagram
• so what concurrent package contents
• BlockingQueue principle
• Thread-safe container
• Thread pool Related: thread pool parameters meaning, how to set the thread pool parameters, how to tune the thread pool
• Inter-range communications: concepts, methods: in Sync synchronization packet, volatile, synchronized, a single multi-threaded embodiment, join
• Thread Synchronization: Concepts
• Deadlock: Principles and solutions, handwriting deadlock
• Comprehensive title (think more difficult, encountered hard luck): Scenic multiple entry exit polls, multi-threaded to ensure that an object, double-check a single case of handwriting, producers and consumers handwriting, handwritten multiple threads execute in sequence
• Optimistic locking Pessimistic locking thought: optimistic and pessimistic locking common implementations (optimistic lock: the version number of mechanisms, CAS algorithm), commonly used optimistic locking so what are pessimistic locking (optimistic locking atomic package under the pessimistic locking synchronized reentrantLock)
• Concurrent access to the wrong solution
• Implemented lock to read write (I can answer them all fours)

database

Ask those on the back to get away, very simple

• Handwritten statement basis
• Affairs (very important !!): isolation level, four characteristics, problems of different isolation levels produced (dirty reads phantom reads Non-repeatable read)
• Stored Procedures | function | triggers: the difference between stored procedures and functions, how to choose; trigger classification
• Storage Engine
• Distinguish the difference between internal and external links about the link: Advanced Search Related
• Index-related (very important !!): principles, advantages and disadvantages of the index, the index design optimization strategy, the type commonly used index, the index take effect scene
• Database (non-indexed) optimization
• When the huge amount of data, how sub-library sub-table, scene, conditions and implementation
• B-tree and B + tree: differences, drawing a B + tree
• Design unlimited classification
• union和union all
• Query results go heavy: the difference between distinct and group by
• Database connection pool: maximum number of connections, the minimum number of connections

JVM

simple

• JVM runtime memory allocation: the ratio of each region is provided
• GC: GC algorithm, heap and GC algorithm; GC time
• finalize method
• Memory leaks generation and solve (strictly speaking, does not belong to jvm knowledge)
• Object Creation Process
• Parameters: turn yourself what JVM parameters
• Class initialization sequence (load connection initialization)
• How to judge the object is garbage
• Recycling Process
• Examples of static variable domain (hell)

algorithm

I have nothing to say algorithm, brush it yourself, here are a classic problem appeared, some of the side door, I do not write

• Sorting algorithm: seven kinds of basic algorithms must be skilled to the handwriting, and the complexity of their characteristics; classic random quick drain and fast exhaust, complexity; to a sequence, after a sequence of handwritten fast discharge
• Stacks and queues: queue and stack difference, using the scene; queue array
• Found 10 billion url appear in most of the k (! Many companies have asked this question to, and should be divided file hash + + heap sort, check it yourself)
• How to remove the tree structured data
• Difference introduced red-black tree, and AVL tree
• Consistent hashing, how to resolve hash collision
• Arrays and linked lists: the difference between arrays and linked lists of advantages and disadvantages; the list to re-; ordered list merge (there have been a few times !!); find an equal number of two arrays, can not use other data structures; an array only two numbers appear once, the other two are present, find the two numbers; given a number and array to identify the array is equal to the sum of the two numbers of the two numbers, the data structure can not be used; find two cross-linked list node
• 1 is a decision tree subtree tree 2
• Binary Tree: hierarchical traversal; postorder; 72 nodes, the number of non-leaf nodes Q; seek distance of any two nodes, the time complexity; determining whether a balanced binary tree, how to adjust the balanced binary tree
• Matrix to find the shortest path, directly drawn
• Handwriting LRU

JDBC & ORM

Is not asked of a region, can ask the less, I had learned a long time wasting

• sql injection and prevention measures (preparestatement and statement difference, so what's the advantage)
• mybatis: how to turn on lazy loading, how paging, mybatis batch query handwriting
• Implementation of database connection pool: Design your own connection pool needs to consider what
• Why not drive the reflective new (present internal static internal block, prevent loaded twice)

spring race

• Introduction springboot / Spring: Do not stiff back ioc and aop, although the main certainly say this, but can easily pull something else ah, such as one-stop spring is a lightweight framework
• Spring used in design patterns: spring how to implement Singleton pattern
• spring isolation level
• Services wrote in that part of the spring (service layer), why not controller or dao layer
• springmvc workflow
• Interceptor Zuosa, with Shashi Hou
• The method of modifying the prototype of spring
• aop of use, when to use jdk dynamic proxy when using cglib (case when not in use Interface) (Do not ask me, ask just do not know)
• How to create a global variable in spring

Design Patterns

• Singleton (very important !! !!): handwritten hungry man and lazy, single cases to ensure that multi-thread-safe manner, dual detection singleton
• Factory pattern, strategy pattern, observer pattern, adapter pattern (more often test)

Operating Systems & Computer Network

I say this part do not know, but still had, alas, thank the interviewer ah

• Subnet Mask effect
• Process scheduling algorithm
• Interprocess communication
• Difference between TCP and UDP (often test !!)
• TCP three grip four play (often test !!)
• HTTP (!! frequently test): Common status codes, http and https, http request content of the response, get and post the difference
• Visit the Web site of the process and protocols related to the corresponding seven-layer model (often test !!)

Project & comprehensive title

Everyone is different in this regard and the low probability of repetition, I have listed a few useful references

• How to write code to ensure fewer mistakes
• How to project the class function declaration
• Project the impression of significant bug, how to solve
• Talk about micro-services, how to micro-management services
• path and classpath difference
• eclipse, intellij shortcuts and tips
• How to ensure the browser request arrives backstage instead of using the browser cache (plus random request parameter)
• Transfer design scene (which is a comprehensive question I asked, flutter Street)
• Design of mobile payment scenarios
• BS and CS
• How to find out why the system Caton
• Many linux waittime What links