static

How does Thread.sleep() work when called from multiple threads

由 北慕城南 提交于 2020-01-21 11:09:09
问题 sleep() is a static method of class Thread. How does it work when called from multiple threads. and how does it figure out the current thread of execution. ? or may be a more generic Question would be How are static methods called from different threads ? Won't there be any concurrency problems ? 回答1: how does it figure out the current thread of execution? It doesn't have to. It just calls the operating system, which always sleeps the thread that called it. 回答2: The sleep method sleeps the

Typescript: how to return subclass type from inherited static property?

由 本小妞迷上赌 提交于 2020-01-21 08:08:39
问题 class BaseDoc { static Collection; static find(){ // which is expected to return an instance of SubDoc when run SubDoc.find() return this.Collection.find(); } } class SubDoc extends BaseDoc {} What I hope is: When running SubDoc.find(), the app knows the type of the return value to be an instance of SubDoc rather than BaseDoc. How can I achieve that? 回答1: You can create a generic version of find that will have the this parameter inferred to the type of the class it's being called on, and use

Typescript: how to return subclass type from inherited static property?

由 筅森魡賤 提交于 2020-01-21 08:05:44
问题 class BaseDoc { static Collection; static find(){ // which is expected to return an instance of SubDoc when run SubDoc.find() return this.Collection.find(); } } class SubDoc extends BaseDoc {} What I hope is: When running SubDoc.find(), the app knows the type of the return value to be an instance of SubDoc rather than BaseDoc. How can I achieve that? 回答1: You can create a generic version of find that will have the this parameter inferred to the type of the class it's being called on, and use

Typescript: how to return subclass type from inherited static property?

由 醉酒当歌 提交于 2020-01-21 08:05:32
问题 class BaseDoc { static Collection; static find(){ // which is expected to return an instance of SubDoc when run SubDoc.find() return this.Collection.find(); } } class SubDoc extends BaseDoc {} What I hope is: When running SubDoc.find(), the app knows the type of the return value to be an instance of SubDoc rather than BaseDoc. How can I achieve that? 回答1: You can create a generic version of find that will have the this parameter inferred to the type of the class it's being called on, and use

Difference between static and const variables [duplicate]

由 北战南征 提交于 2020-01-21 06:34:28
问题 This question already has answers here : What is the difference between Const and Static in C#? (5 answers) Closed 4 years ago . what is the difference between "static" and "const" when it comes to declare global variables; namespace General { public static class Globals { public const double GMinimum = 1e-1; public const double GMaximum = 1e+1; } } which one is better (considering that these variables wont be changing ever) namespace General { public static class Globals { public static

java static initialization with inheritance

由 ▼魔方 西西 提交于 2020-01-21 06:13:29
问题 public class Main { public static void main(String[] args) { System.out.println(B.x); } } class A { public static String x = "x"; } class B extends A { static { System.out.print("Inside B."); } } Question: Why output will be: x . But not: Inside B.x 回答1: The reference to B.x issues the following bytecode: getstatic #3 <Field int B.x> According to Java Virtual Machine Spec The Java virtual machine instructions anewarray, checkcast, getfield, getstatic , instanceof, invokedynamic,

Django：static静态文件（css等）的处理

由 烂漫一生 提交于 2020-01-21 04:11:20
1 更目录下建立static包，把css文件拉进去 2 settings文件里添加： STATIC_ROOT = os.path.join(BASE_DIR, "static/") # STATICFILES_DIRS = ( os.path.join(BASE_DIR, 'static'), ) 然后在界面页快捷键option+r，打开manage.py shell，执行命令： collectstatic 3 settings文件里处理： # STATIC_ROOT = os.path.join(BASE_DIR, "static/") STATICFILES_DIRS = ( os.path.join(BASE_DIR, 'static'), ) 4 html中引用： {% load static %} <meta http-equiv="content-type" content="text/html; charset=utf-8"/> <link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css"> <link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap

Why can static member function definitions not have the keyword 'static'?

由 左心房为你撑大大i 提交于 2020-01-21 03:59:29
问题 As per this link on the 'static' keyword in C++ : The static keyword is only used with the declaration of a static member, inside the class definition, but not with the definition of that static member . Why is the static keyword prohibited on member function definitions? I do understand that re-declaring a function as 'static' at its definition is redundant. But using it should be harmless during compilation of the function definition as it does not result in any kind of ambiguity. So why do

Initializing static array of strings (C++)?

由 我只是一个虾纸丫 提交于 2020-01-21 01:15:47
问题 I can't for the life of me figure out how to do this properly. I have a class that needs to store some constants (text that corresponds to values in an enum type) - I have it declared like this (publicly) in my class: const static char* enumText[]; And I'm trying to initialize it like this: const char* MyClass::enumText[] = { "A", "B", "C", "D", "E" }; However gcc gives me the following error: 'const char* MyClass::enumText[]' is not a static member of 'class MyClass' What am I doing wrong?

SpringContextHolder类

由 橙三吉。 提交于 2020-01-20 23:46:21
1、通常使用SpringContextHolder类获取bean实例： 解决： 如果要在静态方法中调用某一bean的方法，那么该bean必须声明为static的，但正常情况下@Autowired无法注入静态的bean,。 利用Spring的使用SpringContextHolder工具类的getBean方法来获取静态bean。 /** * 以静态变量保存Spring ApplicationContext, 可在任何代码任何地方任何时候取出ApplicaitonContext. * */@Service@Lazy(false)public class SpringContextHolder implements ApplicationContextAware, DisposableBean { private static ApplicationContext applicationContext = null; private static Logger logger = LoggerFactory.getLogger(SpringContextHolder.class); /** * 取得存储在静态变量中的ApplicationContext. */ public static ApplicationContext getApplicationContext() {
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