reference

问题 I have some data structures, and I would like to use one as a temporary, and another as not temporary. ArrayList<Object> myObject = new ArrayList<Object>(); ArrayList<Object> myTempObject = new ArrayList<Object>(); //fill myTempObject here .... //make myObject contain the same values as myTempObject myObject = myTempObject; //free up memory by clearing myTempObject myTempObject.clear(); now the problem with this of course is that myObject is really just pointing to myTempObject , and so once

问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 6 years ago . How do I keep some sort of link to a class' property and then use that to access an instance's property? Thing is there are no class instances where the link is created. The idea is to remember the property

问题 In a little game I have to make for college I render a menu at runtime, using movieclips i made of buttons i drawed in illustrator. I imported the illustrator file in flash professional like I always do, and made a AS linkage like I do with my other movieclips that run fine. But when I try to render these buttons I get a error 1009, a null reference. I use AS3 by the way. private function initMenuComponents():void{ var btnPlay:MovieClip = new Play(); var btnOptions:MovieClip = new Options();

问题 In a little game I have to make for college I render a menu at runtime, using movieclips i made of buttons i drawed in illustrator. I imported the illustrator file in flash professional like I always do, and made a AS linkage like I do with my other movieclips that run fine. But when I try to render these buttons I get a error 1009, a null reference. I use AS3 by the way. private function initMenuComponents():void{ var btnPlay:MovieClip = new Play(); var btnOptions:MovieClip = new Options();

问题 In a little game I have to make for college I render a menu at runtime, using movieclips i made of buttons i drawed in illustrator. I imported the illustrator file in flash professional like I always do, and made a AS linkage like I do with my other movieclips that run fine. But when I try to render these buttons I get a error 1009, a null reference. I use AS3 by the way. private function initMenuComponents():void{ var btnPlay:MovieClip = new Play(); var btnOptions:MovieClip = new Options();

问题 In a little game I have to make for college I render a menu at runtime, using movieclips i made of buttons i drawed in illustrator. I imported the illustrator file in flash professional like I always do, and made a AS linkage like I do with my other movieclips that run fine. But when I try to render these buttons I get a error 1009, a null reference. I use AS3 by the way. private function initMenuComponents():void{ var btnPlay:MovieClip = new Play(); var btnOptions:MovieClip = new Options();

问题 Consider the following code: internal class A { public int X; } private void test() { A[] Collection = new A[2]; Collection[0].X = 1; Collection[1] = Collection[0] Collection[0] = new A(); Collection[0].X = 2; //The code above produces: Collection[1] displays 2, and Collection[0] displays 2. //Wanted behaviour: Collection[1] should display 1, and Collection[0] display 2. } Since the array of classes, Collection , is a reference type. Collection[0] points to same memory region that Collection

问题 I have a project that I created that only shows 1 form and button. What I am trying to do is once the button is clicked, it opens a pre-built excel workbook. The problem is, I need to add the excel file within the application bundle. For example, I give the application disc to someone else to load on another computer, and then they can run the application to open the workbook. I know how to reference the file on my personal computer, just not how to add it "within" the project, to be, more or

问题 Can somebody clealry explain me the concept behind multiple reference and dereference ? why does the following program gives output as 'h' ? int main() { char *ptr = "hello"; printf("%c\n", *&*&*ptr); getchar(); return 0; } and not this , instead it produces 'd' ? int main() { char *ptr = "hello"; printf("%c\n", *&*&ptr); getchar(); return 0; } I read that consecutive use of '*' and '&' cancels each other but this explanation does not provide the reason behind two different outputs generated

问题 As I understand it, one cannot change the reference variable once it has been initialized. See, for instance, this question. However, here is a minmal working example which sort of does reassign it. What am I misunderstanding? Why does the example print both 42 and 43? #include <iostream> class T { int x; public: T(int xx) : x(xx) {} friend std::ostream &operator<<(std::ostream &dst, T &t) { dst << t.x; return dst; } }; int main() { auto t = T(42); auto q = T(43); auto &ref = t; std::cerr <<