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How is the expiration time of 1.redis set? JD.com will never expire.

How many data types are there? 5 species

String binary secure jpg or serialized object

Set unordered and unrepeatable sets

List first in first out

Hash storage object

Zset ordered set

K score v ranking

Zrange

Persistence mechanism?

Dubbo 2.56

The implementation principle of 2.synchronized locks the object.

Implemented by jvm

Differences in implementation classes between 3.synchronized and ReentryLock

Why should 4.wait notify be used together?

5. What happens if there is no matching object hierarchy

An exception will be reported when called separately

The wait (), notify (), and notifyAll () methods of an object can be called only if the calling thread has an exclusive lock on that object. This usually goes unnoticed by programmers because program validation usually calls them in an object's synchronization method or block of synchronization code. If you try to call these three methods when the object lock is not acquired

"java.lang.IllegalMonitorStateException:current thread not owner".

The bottom layer uses the object as a monitor.

6. Thread pool parameters?

7. Concurrent package thread pool thread interaction

8. Collection class

The implementation class HashSet LinkedHashSet TreeSet of set

9.hashset and hashmap

Four construction methods of 10.hashmap

11. The purpose of load factor: space for time to reduce collision

twelve。 When will the expansion be carried out?

13. What is the range of load factor?

14.hashmap is not thread safe? Why?

How does 15.concurrenthashmap achieve thread safety?

16. The granularity of the lock?

17.jvm partition?

Part of the heap new

Stack reference address

Method area

Is 18.java value passing or reference passing?

Integer i114125

Integer i2o125

= = is it true or false?

Within the range of values is true

19. What happens if the level of recursion is too deep?

20. How to write the singleton pattern? Double-ended retrieval DCL, enumeration, anonymous inner class

Instantiate the lazy object when it is used

21. How to ensure thread safety?

Volatile (instruction rearrangement) + synchronize

22.Threadlocal application environment

Implicitly passing parameters ensures thread isolation and thread closure

23. Low-level implementation?

24. Quarantine level? Repeatable read uncommitted read submitted serialization

Multiple transaction execution does not affect each other

Low efficiency

Gap and row locks are added to solve the problem of phantom reading.

25. Seven-layer transmission of the network

DNS: homologous policy

twenty-six。 How to generate uuid in distributed Environment

Distributed locks?

Redis increment

Take out a few bits of the unique code of the machine and save it as the machine id

Zk collaborative generation

twenty-seven。 Optimistic lock pessimistic lock

Application scenario

twenty-eight。 How to solve the failure of inventory reduction and update?

Retry

The performance of optimistic lock is low

29.Spring configuration singleton scope

thirty。 Can there be anything else between single case and multiple cases?

Request session

Single case and multiple cases

thirty-one。 How to implement the Management transaction AOP

@ Aspectj dynamic implantation

thirty-two。 What is the difference between a dynamic agent and a static agent?

The underlying layer of dynamic proxy is actually the reflection mechanism of java. The most representative feature of static agents is reflected in the simple factory model.

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