• Why not recommend using UTF-8 in MySQL?


    I remember last year when I was saving Emoji expressions into mysql, I kept making mistakes and couldn’t import them. Then we found a way — by puttingutf8Change toutf8mb4It’s OK. I didn’t delve into it. A year later, I saw an article saying that Emoji text takes up 4 bytes and usually needs to be […]

  • Java MySQL BLOB data read / write operation


    ​ package com.lw.database; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; /** * CREATE: CREATE TABLE IDCard ( id char(18),pic BLOB); * @author fhadmin * from www.fhadmin.cn */ public class LOBTest { protected static final String DEFAULT_URL = “jdbc:mysql://”; protected static final String DRIVER_NAME = […]

  • [rust] basic data type


    This article introduces the built-in data types provided by rust. Boolean type Boolean typeLogical values representing yes and No. It has two values:trueandfalseGenerally used in logical expressions, and, or, and not operations can be performed: fn main() { let x = true; let y: bool = ! x; // False, inverse operation let z = […]

  • Use docker to manage the web assembly program written in rust


    Developers can deploy, manage and run lightweight web assembly applications in wasedge through docker tools such as dockerhub and cri-o. WasmEdgeByManaged by CNCF (cloud native Computing Foundation)The web assembly runtime is the execution sandbox for edge computing applications. Although web assembly was originally invented as the runtime of browser applications, its lightweight and high-performance sandbox […]

  • Use of cut command


    cutIt is used to intercept a part of each line of file or standard input. usecutYou must specify one of the following three options: -b byte-listIntercept by byte-c character-listIntercept according to characters-f field-listIntercept according to paragraph The above three parametersbyte-list character-list field-listIs one or more numbers and ranges separated by commas-Range of connections). The actual […]

  • #Progma pack (x) description


    1. Byte alignment (memory dependent) In modern computers, the memory space is divided according to bytes. Theoretically, it seems that the access to any type of variables can start from any address, but the actual situation is that when accessing a specific variable, it is often accessed at a specific memory address, which requires various […]

  • MySQL official documents learn char and varchar of data types


    Char and varchar types are similar, but they are also different in storage and retrieval, and they are also different in maximum length and whether to keep spaces at the end. The length of char is defined by yourself when you create the table. The range of length is 0-255. When the char value is […]

  • How strong is the 10W word Alibaba internal Java interview manual that makes GitHub bow?


    First of all, some people will ask why Ali’s internal information is written in the title of the article? Here’s an explanationAfter reading this, I don’t need to say more. Although I don’t know if it’s true, I also read this document and summarized the following contentsInterviewContains(Basic + JVM + multithreading & concurrency + Spring […]

  • Architecture and operating system


    Architecture and operating system Part 1. Architecture foundation 1. Von Neumann architecture All data and instructions processed by computer are represented by binary numbers Sequential execution program In the process of computer operation, the program to be executed and the data to be processed are first stored in the main memory (memory). When the computer […]

  • If you don’t understand the Java class loading mechanism, I suggest you take a look at the notes summarized by Alibaba technical officer!


    Class loading mechanism The class file is loaded into the memory, and the data is checked, prepared, parsed and initialized to form a bytecode that can be directly used by the virtual machine Timing of class loading (trigger class initialization) Instantiating objects with the new keyword Read a static block of code for a class […]

  • String length limit


    Is there a limit to the length of string? How much is it? In Java, string is limited in length, and there are specifications in JVM compilation.String actually uses an array of char type to store the characters in the string. public final class String implements java.io.Serializable, Comparable<String>, CharSequence, Constable, ConstantDesc { @Stable private final […]

  • How to learn about Clickhouse


    1、 Introduction 1.1 what is Clickhouse? Clickhouse is an open source database based on column storage for real-time data analysis by yandex (the largest search engine in Russia). Its data processing speed is 100-1000 times faster than traditional methods. The performance of Clickhouse is better than that of column oriented DBMS in the market. Each […]