static-members

问题 I have two Activities. And a static integer called as counter. So if I press a button in activity ' A ' then counter = counter + 1 . Here is the code from activity a: public static int counter = 0; cmdOk.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { counter = counter + 1; if (counter == 5) { tagihan.txtShip1.setTextColor(Color.parseColor("#000000")); tagihan.txtNilai1.setTextColor(Color.parseColor("#000000")); tagihan.txtSupir1.setTextColor(Color

问题 I have two Activities. And a static integer called as counter. So if I press a button in activity ' A ' then counter = counter + 1 . Here is the code from activity a: public static int counter = 0; cmdOk.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { counter = counter + 1; if (counter == 5) { tagihan.txtShip1.setTextColor(Color.parseColor("#000000")); tagihan.txtNilai1.setTextColor(Color.parseColor("#000000")); tagihan.txtSupir1.setTextColor(Color

问题 I was pointed last week about a piece of code like this: #include <pthread.h> namespace NSTest { class SingletonClass { public: static SingletonClass & getInstance() { static pthread_mutex_t mutex; pthread_mutex_lock(&mutex); if(singletonPtr==nullptr) { createInstence(); } return (*singletonPtr); pthread_mutex_unlock(&mutex); } private: static void createInstence() { static SingletonClass static_SingletonClass; singletonPtr=&static_SingletonClass; } static SingletonClass * singletonPtr; };

问题 I was pointed last week about a piece of code like this: #include <pthread.h> namespace NSTest { class SingletonClass { public: static SingletonClass & getInstance() { static pthread_mutex_t mutex; pthread_mutex_lock(&mutex); if(singletonPtr==nullptr) { createInstence(); } return (*singletonPtr); pthread_mutex_unlock(&mutex); } private: static void createInstence() { static SingletonClass static_SingletonClass; singletonPtr=&static_SingletonClass; } static SingletonClass * singletonPtr; };

问题 I am trying to access a static member from a non-static function in the class, and I get an error saying Static member cannot be accessed off an instance variable this is how my code looks - class myClass { public static testStatic: number = 0; public increment(): void { this.testStatic++; } } From what I understand of static members/methods, we shouldn't access non-static members in static functions, but vice-versa should be possible. the static member is already created and is valid, so why

问题 1) If I'm not mistaken, C++ standard guarantees that static variables in a single translation unit are initialized in their definition order. And I'm confused about the following code fragment: extern int n; int k = n; int n = 2; extern int n; is the declaration, not the definition, so k is defined before n , but GCC, Clang and MSVC all show me that k == 2 after the initialization of the global variables. For me it's unclear how can k be assigned 2 after int k = n; , because n is not

问题 This question already has answers here : In Java, are enum types inside a class static? (2 answers) Closed 4 years ago . What's the difference between static and non-static enum in Java? Both usages are same. Is it correct that all static ones are loaded on memory on startup, and non-static ones are loaded on demand ? If yes, then which method is better? Keeping some data always in memory or using server resources to load them each time? public class Test { public enum Enum1 { A, B } public

问题 I have a class Car which has a class scope variable cost, i understand that this is a bad idea in practice, just trying to understand the effects of public scope class variables. Will cost be accessible and modifiable by all objects of class Car, references by Car.cost, throughout all class loaders, or should i be aware of circumstances where multiple copies of Car.cost might exist? Will there be just one Car.cost in any given circumstance? public class Car{ public static int cost; public Car

问题 I have a template singleton class, with a static instance, and a static getInstance() method. However, I'm getting an undefined reference error on the instance from g++ (MinGW); at first, I thought it was linker-order error, but I get the same thing no matter which order I put them in. However, I found that if I explicitly specialize the instance, it does compile (which isn't an acceptable solution). So, here's the code: Singleton.hpp: #ifndef SINGLETON_HPP #define SINGLETON_HPP #include

问题 class A { public static $foo = 42; } $class = 'A'; $attribute = 'foo'; var_dump(isset($class::$attribute)); //gives bool(false) How can i checkt, of this static attribute exists in this class? 回答1: Use variable variables: var_dump(isset($class::$$attribute)); // the two dollars are intentional If you don't have PHP 5.3 yet the only accurate way is probably using the Reflection API: $reflectionClass = new ReflectionClass($class); $exists = $reflectionClass->hasProperty($attribute) &&