1. What is the default cluster fault tolerance scheme for Apache Dubbo? (radio)
A. Failover Cluster
B. Failfast Cluster
C. Failsafe Cluster
D. Failback Cluster
2. What is wrong with Kafka? (pops)
A. Messages are divided by topic. A topic is A queue, and A topic can have multiple consumers. When the producer sends A message in A topic, all consumers who subscribe to this topic can receive the message
B. Kafka maintains multiple partitions for each topic to ensure that messages are consumed in an orderly manner
C. All message reads and writes are performed in the primary partition. Other replica partitions only copy data from the primary partition
D. Messages can be sent in three modes: synchronous, asynchronous, and Oneway. Asynchronous is the default mode
3. The following description of the sorting algorithm is correct :(multiple selection)
A. Bubble sort and insert sort are both stable sorting algorithms
B. If the array is sorted in order, use insert sort, time order is O(n)
C. Quicksort Selecting the maximum value as a reference value can speed up the sorting process
D. The best case of quicksort is O(nlogn)
4. Which of the following statements about the JVM is true? (pops)
A. A program counter is A small memory area that indicates the line of bytecode executed by the current thread and is thread-isolated
B. Virtual machine stack describes the memory model of Java method execution, which is used to store local variables, operand stack, dynamic links, method exits and other information. It is thread isolated
C. The method area is used to store data such as JVM loaded class information, constants, static variables, and compiled code by the compiler, which is shared by threads
D. The heap is shared by all threads in order to hold object instances, and almost all object instances are allocated here. An OOM exception is raised when there is no available heap memory
5. What is true about the TCP shutdown process? (pops)
A. The connection in TIME_WAIT state is closed after 2MSL
B. For an ESTABLISHED TCP connection, call the close interface before the shutdown function to enable the active caller to enter the semi-closed state
C. The end that sends a FIN message enters the CLOSING state. The end cannot send or receive a FIN message before receiving an ACK from the peer party, and cannot send or receive a FIN message after receiving an ACK from the peer party
D. Although TCP is reliable, packet loss may occur on a TCP connection that has been successfully established
6. Which of the following is true about B+ trees being better than B trees for indexing? (pops)
A. There are Pointers connected between leaf nodes, so B + tree is more suitable for range retrieval;
B. A non-leaf node stores only keywords and Pointers. If a non-leaf node has the same size, a B + tree can contain more keywords, reducing the tree height and reducing the disk read/write cost during query.
C. The query efficiency of B+ tree is stable. Any keyword lookup must take a path from root to leaf. The length of all keyword query paths is the same and the efficiency is the same.
D. On the non-leaf node, a pointer pointing to a non-leaf node at the same layer is added to improve the minimum utilization of the node from 1/2 to 2/3
7. What is true about Netty? (pops)
A. Netty thread model adopts the separation of “server listener thread” and “IO thread”
B. Generally, in NIO non-blocking mode, Netty assigns an EventLoop to each Channel and processes events throughout its life cycle by this EventLoop
C. An eventLoop can bind multiple channels
D. Generally, when receiving messages, the messages will be submitted to the business thread pool for processing after being processed by pipeline
8. What is the correct call order when MyBatis executes SQL? (radio)
1) SqlSessionFactory
(2) the SqlSession
(3) StatementHandler
(4) ParameterHandler
(5) ResultSetHandler
6 Executor
All landowners TypeHandler
A. (1) (2) (3) (4) (5) 6. 7
B. (1) (2) and (3) (4) 7 (5)
C. (1) (2) (4) (7) 6 (5)
D. (1) (2) (3) 7 (4) and (5)
9. What are the correct steps for submitting tasks to a thread pool? (radio)
① Determine whether the maximum number of threads set by the thread pool is reached. If not, create a new thread to execute the task
② Check whether the number of threads in the thread pool is greater than the set number of core threads and create a core thread to execute the task
③ Check whether the buffer queue is full. If not, put the buffer queue into the queue for execution
(4) Execute the reject policy
A. (2) (1) (3) (4)
B. (2) (3) (1) (4)
C. (1) (2) (3) (4)
D. (1) (3) (2) (4)
10. Which of the following is wrong about the loading mechanism of the class (single option)
A. Class loading refers to reading the bytecode from the compiled class file into memory, placing it in the heap and creating the corresponding class object
B. Loading is the process of loading files into memory. Find such a bytecode file by its fully qualified name and create a Class object from the bytecode file
C. In the preparation phase, memory is allocated. Allocate memory for class variables, that is, static variables in the class, and set the initial value, which is 0 or NULL, rather than the specific value set in the code
D. Parse fields, interfaces, and methods. Basically, the process of replacing symbolic references in a constant pool with direct references. A direct reference is a pointer to a target, relative offset, and so on
Click here for a breakdown of the answers