Here is a summary of the high-frequency questions collected on the Internet. I hope to help you reach the interview status quickly. This post will continue to be updated, so stay tuned. If you feel that the format is ok, please like and bookmark it. If you have any comments and suggestions, please leave a message in the comment area~
- The difference between process and thread?
- What are the scheduling algorithms for processes? (main)
- Common IO model?
- What is the difference between select, poll and epoll? The data structure used at the bottom of epoll.
- What are the communication methods of the process? What about threads?
- What does the fork function do?
- The concept of coroutine?
- Linux processes and threads?
- View the occupied port by process id, and view the occupied process id by port number?
- How to check the processes that take up more memory?
- What causes the zombie process?
- What caused the orphan process?
- Talk about virtual memory. What is the relationship between virtual memory and physical memory?
- Talk about segmentation and paging? And the corresponding scene?
- Talk about user mode and kernel mode? Will all system calls enter the kernel mode?
- What linux commands are commonly used? How to open a file and search for a certain word? How to find files containing txt in a certain directory?
- Have you used the ping command? Briefly introduce. What does TTL mean?
- How to judge whether a host opens a certain port?
- Talk about the more mode you use most (the factory mode and the observer mode I said), and then implement a singleton mode.
- Which sorting algorithms are stable, why is direct insertion sorting stable, and the time complexity and space complexity of various sorting algorithms?
- How to implement non-recursive algorithms for various traversals of binary trees? Briefly tell.
- Hard link and soft link?
- Classification of interruptions?
- Soft interrupt and hard interrupt?
- Red-black tree and balanced binary tree?
- StringBuilder 和 StringBuffer
- Java realizes the memory allocation of contiguous space?
- What are the ways to create objects?
- What is the difference between an interface and an abstract class?
- What is the difference between deep copy and shallow copy?
- Talk about encapsulation, inheritance, polymorphism (important).
Compile-time polymorphism
Run-time polymorphism - What is generic? Type erasure?
- How to implement static proxy? What is wrong?
- The role of dynamic agents? Where is it used? (AOP and RPC frameworks are all used, and a dynamic agent is often required to be handwritten in the interview written test)
- What is the difference between JDK's dynamic proxy and CGLIB?
- Talk about the understanding of Java annotations, what problems have been solved?
- Java reflection? What are the disadvantages of reflection? How do you understand reflection (why does the framework need reflection)?
- Why does the framework need reflection technology?
- Two ways to obtain Class objects
- Scenarios of memory leaks and memory overflows.
Memory leak scenario
Memory overflow scenario - Let me talk about strong references, weak references, soft references, and phantom references.
- Whether an object has a phantom reference will not affect its lifetime, and an object cannot be obtained through a phantom reference.
- Tell me about Java's NIO, AIO, BIO?
- The use of finalize() method in Java?
- What are the GC Root objects
- What is the difference between Class.forName and ClassLoader in Java?
- Talk about CopyOnWriteArrayList and CopyOnWriteArraySet?
CopyOnWrite container:
the disadvantages of CopyOnWrite - Singleton mode (important)
- The difference between >> and >>> in Java
- Why is the network hierarchical?
- Do you understand the TCP/IP 4-layer model?
- Which layer of protocol is HTTP? http common status codes
- What is the difference between HTTP and HTTPS?
- Talk about symmetric encryption algorithm and asymmetric encryption algorithm?
- HTTP2.0 talk about
- Detailed explanation of HTTP messages? Tell me more about the request message and the difference between HTTP and TCP
- What is the TCP three-way handshake process and the reason for the three-way handshake?
- How did TCP wave four times, and why?
- What does TCP sliding window do? Where is the reliability of TCP? How is congestion control achieved?
- What is the difference between TCP and UDP? And its applicable scenarios.
- The difference between Mac address and ip address? Now that I have a Mac address, why do I need an IP address?
- What process do you need to go through when you open an e-commerce website? What protocols are used respectively.
- The email sending process?
- DNS resolution process, do you understand DNS hijacking?
- What is the difference between GET and POST?
- Problems with session and cookie?
- HTTP is a protocol that does not save state, how to save user state?
- Arp agreement?
- Do you understand DDos attacks?
- The expansion mechanism of ArrayList?
- When the underlying implementation of HashMap, JDK 1.8, why convert the linked list into a red-black tree? Load factor of HashMap
- The underlying implementation of ConcurrentHashMap
- What read operation of ConcurrentHashMap does not require locking?
- What is the difference between HashMap, LinkedHashMap and TreeMap? HashMap, TreeMap,
- Which collections are thread-unsafe, and which collections are thread-unsafe? How to solve it? Thread-safe collection class.
- What is fail-fast, can you give me an example? What is fail-safe?
- HashMap multi-threaded operation causes infinite loop problem abnormal
- How to ensure thread safety in the case of multithreading.
- Write a deadlock example
- Talk about the role of the volatile keyword.
- The role of synchronized, talk about the underlying implementation.
- The difference between ReetrantLock and synchronized
- Talk about the difference between the synchronized keyword and the volatile keyword
- ReetrantLock implementation
- What is the difference between interrupt, interrupted and isInterrupted? How to stop a running thread
- The role of thread pool? What are the parameters of the Java thread pool? How many kinds of blocking queues are there? What are the rejection strategies? How does the thread pool work?
- In what scenarios are the thread pool rejection strategies used?
- Thread deadlock, what are the ways to release thread deadlock? (I fell on this question twice, it took too long and I forgot, how to solve it is very important)
- What is ThreadLocal, what is the application scenario, and what is the principle?
- Why should ThreadLocal class be decorated with private static?
- What are the flaws of ThreadLocal? What is the problem if the threads of the thread pool use ThreadLocal?
- Introduce what locks Java has
- Talk about optimistic lock and pessimistic lock, and where are they used.
Interview Question Answer
Alright guys, this is the end of this article! Regarding why the answers to the interview questions are not written directly, what I want to say is that writing the interview questions will make the article very long (it is already very long...) This will affect the readability of the article.
This article is shared with friends who need to interview and brush up questions, and I wish you all the best to get the offer you want. This information mainly includes Java basics, data structures, jvm, multithreading, etc. Due to limited space, only a small part is shown below. Interview questions, friends who need the full version can click a little link to jump to receive, link: click here to download the answer for free, get code: CSDN
