Tag:data type

  • Go – map set

    Time:2021-3-4

    summary A map set is an unordered key value data structure. The key / value in the map set can be of any type, but all keys must belong to the same data type, all values must belong to the same data type, and the data types of key and value can be different.Declaration map […]

  • Parquet reading and writing of column storage format

    Time:2021-2-24

    summary Apache parquet is a column storage format that can be used by any project in Hadoop ecosystem, with higher compression ratio and smaller IO operation. Many people need to install Hadoop locally to write parquet on the Internet. Here is a way to write parquet file without installing Hadoop, and two ways to read […]

  • IOS strong reference

    Time:2021-2-24

    KCPerson.h #import @interface KCPerson : NSObject @property (nonatomic,assign) int no; @end KCPerson.m #import “KCPerson.h” @implementation KCPerson -(NSString *)description{ return [NSString stringWithFormat:@”no=%i”,_no]; } @end main.m #import #import “KCPerson.h” int main(int argc, const char * argv[]) { @autoreleasepool { //strong __strong KCPerson *person1=[[KCPerson alloc]init]; __strong KCPerson *person2=person1; person1.no=1; Nslog (@ “% @”, person2); // result: no = […]

  • Basic packaging types

    Time:2021-2-23

    Basic wrapper type is to wrap simple data type into complex data type. var str = ‘andy’; console.log(str.length); Only objects and complex data types have attributes and methods. Why is there a length attribute? The process is as follows Var temp = new string (‘andy ‘); / / wrapped as complex data type STR = […]

  • Reactive spring: responsive redis interaction

    Time:2021-2-22

    This article shares how to implement redis responsive interaction mode in spring. This paper will simulate a user service and use redis as the data storage server.This article involves two Java beans, users and interests public class User { private long id; private String name; //Label private String label; //Receiving address longitude private Double deliveryAddressLon; […]

  • Go – structure

    Time:2021-2-21

    summary A structure is an aggregate data type that combines zero or more variables of any type. It can also be regarded as a collection of data.Declaration structure   //demo_11.go package main import ( “fmt” ) type Person struct { Name string Age int } func main() { var p1 Person p1.Name = “Tom” p1.Age […]

  • A guide to Gemeng’s new HTML5 (2)

    Time:2021-2-21

    We have already introduced it to you in the last articleNew content and basic page layout in HTML5This article will continue to introduce another component of HTML5 in a broad sense: Javascript data types. As a weakly typed language, JavaScript is characterized by dynamic typing. That is to say, you don’t need to declare the […]

  • Java Basics: a deeper understanding of reflection

    Time:2021-2-20

    reflex Reflection is the soul of frame! But first get the class type object corresponding to each bytecode file 1. Overview The java reflection mechanism is based onrunning state For any class, you can know all the properties and methods of the class; for any object, you can call any of its methods and propertiesDynamic […]

  • [reprint] SQL server user defined functions

    Time:2021-2-20

    Original address:https://docs.microsoft.com/zh-cn/previous-versions/aa686015(v=msdn.10)?redirectedfrom=MSDN SQL server user defined functions 2013/06/05 John Papa A user-defined function (UDF) is a prepared code fragment that can take parameters, process logic, and then return some data. According to SQL Server Books Online, SQL Server ™ UDF in 2000 can accept any number of parameters from 0 to 1024, but I must […]

  • Learning MySQL

    Time:2021-2-20

    Basic concepts of database 1. English word of database: database, abbreviation: dB 2. What database? *A warehouse for storing and managing data. 3. Characteristics of database 1. Persistent storage of data. In fact, a database is a file system 2. Convenient storage and management of data 3. Using a unified way to operate the database […]

  • Dart tutorial 01 – variables, types, functions

    Time:2021-2-18

    Hello World Salute the classic ‘hello world’ program. Like Java, every dart program must have a main as its entry point. To run the program, save it in a file called “hello”_ world.dart ”And execute the following command in the terminal. (if there is no dart environment, complete the installation first.) Defining variables Just as […]

  • The difference between object, VaR and dynamic in C

    Time:2021-2-15

    Link to the original text:Difference Between Object and Dynamic Keyword in C#Difference between var and dynamic in C# Chapter 1 (the difference between dynamic and object) We often see that many C # developers can’t distinguish between object and dynamic variables. I recently tried to find related tutorials and articles on the Internet, but I […]