Programmer Think

1key and value are allowed to be null; 2key will be overwritten if repeated, and value can be repeated; 3. Orderly; 4LinkedHashMap is non thread safe; 1 LinkedHashMap can be considered as HashMap+LinkedList, that is, it uses HashMap to operate data structures and LinkedList to maintain the sequence of inserted elements 2 the implementation ide ...

Multi table query classificationCategory 1: equivalent connection vs non equivalent connection1. Equivalent connectionSELECT employees.employee_id, employees.last_name, employees.department_id, departments.department_id, departments.location_id FROM employees, departments WHERE employees.department_id = departments.department_ ...

The AspectJ Pointcut syntax is very detailed Classified pointcuts follow a specific syntax to capture the usable join points of each kind. Main types: Method execution: execution(MethodSignature) Method call: call(MethodSignature) Constructor execution: execution(ConstructorSignature) Constructor call: call(ConstructorSignature) Class initiali ...

What is Spring Cloud Square When talking about Spring Cloud ecology, you must be familiar with Feign. As shown in the figure below, Feign can hide the Rest requests of the underlying (okhttp, httpclient) and pretend to be similar to the Controller of spring MVC. You don't have to splice URLs, splice parameters and other operations by yourself. ...

preface Take notes and share some common Vue3 new features and which methods have changed. I only write some commonly used here. For more, please see the Vue3 official website here Interested parties can pay attention to the official account: front-end entertainment. Component v-model support parameters In vue2 When x, if we want to pass v ...

Factory mode effect: It realizes the separation of creator and caller Detailed classification: Simple factory mode It is used to produce any product in the same hierarchical structure (for adding new products, the existing code needs to be overwritten) Factory mode method It is used to produce fixed products with the same level struct ...

catalogue 1, APT introduction 2, Supply mode of APT source 3, Local APT source 1. Use the DEB package of the CD as the APT source 2. The file source list is used as the system installation source 3. View profile 4. Update repository index 4, Network APT source 1. Backup profile 2. Write configuration file 1) Aliyuan (ubuntu 16.04) 2 ...

  Today, we bring you the design of real-time image edge detection system based on FPGA. Due to the long length, it is divided into three parts. Today, I'll bring the third and second articles. I don't talk much and deliver the goods. Reading guide With the rapid development of science and technology, FPGA brings new opportunities for digi ...

SSH (secure shell) is the most common remote management protocol for Linux based systems, routers, switches, firewalls, devices and other assets. Although the SSH daemon provides Excellent enhancements, Your to enhance Authentication method and access control However, SSHD does not provide native monitoring. This blog post details how to use I ...

Development tools: mysql-8.0DataGrip Data source: Chapter7 csv id,name,sales_A,sales_B,price_A,price_B E001,Zhang Tong,18,15,10,5 E002,Li Gu,12,17,10,5 E003,Sun Feng,19,20,10,5 E004,Zhao Heng,12,14,10,5 E005,Wang Na,13,11,10,5 E006,Li Wei,16,16,10,5 E007,Liu Jie,11,13,10,5 E008,Xue Li,14,18,10,5 E009,Pei Jun,11,18,10,5 (1) Arithmetic o ...