using-statement

问题 Does Java have a using statement that can be used when opening a session in hibernate? In C# it is something like: using (var session = new Session()) { } So the object goes out of scope and closes automatically. 回答1: Java 7 introduced Automatic Resource Block Management which brings this feature to the Java platform. Prior versions of Java didn't have anything resembling using . As an example, you can use any variable implementing java.lang.AutoCloseable in the following way: try

问题 In the example below, is the connection going to close and disposed when an exception is thrown if it is within a using statement? using (var conn = new SqlConnection(\"...\")) { conn.Open(); // stuff happens here and exception is thrown... } I know this code below will make sure that it does, but I\'m curious how using statement does it. var conn; try { conn = new SqlConnection(\"...\"); conn.Open(); // stuff happens here and exception is thrown... } // catch it or let it bubble up finally {

问题 Which one: using (var myObject = new MyClass()) { try { // something here... } catch(Exception ex) { // Handle exception } } OR try { using (var myObject = new MyClass()) { // something here... } } catch(Exception ex) { // Handle exception } 回答1: I prefer the second one. May as well trap errors relating to the creation of the object as well. 回答2: Since a using block is just a syntax simplification of a try/finally (MSDN), personally I'd go with the following, though I doubt it's significantly

问题 I\'m trying to calculate the distance between two points. The two points I stored in a vector in C++: (0,0) and (1,1). I\'m supposed to get results as 0 1.4 1.4 0 But the actual result that I got is 0 1 -1 0 I think there\'s something wrong with the way I use iterator in vector. How can I fix this problem? I posted the code below. typedef struct point { float x; float y; } point; float distance(point *p1, point *p2) { return sqrt((p1->x - p2->x)*(p1->x - p2->x) + (p1->y - p2->y)*(p1->y - p2-

问题 I\'ve got a bunch of properties which I am going to use read/write locks on. I can implement them either with a try finally or a using clause. In the try finally I would acquire the lock before the try , and release in the finally . In the using clause, I would create a class which acquires the lock in its constructor, and releases in its Dispose method. I\'m using read/write locks in a lot of places, so I\'ve been looking for ways that might be more concise than try finally . I\'m interested

问题 This question already has answers here : What are the uses of “using” in C# (29 answers) Closed 4 years ago . What is the purpose of the Using block in C#? How is it different from a local variable? 回答1: If the type implements IDisposable, it automatically disposes it. Given: public class SomeDisposableType : IDisposable { ...implmentation details... } These are equivalent: SomeDisposableType t = new SomeDisposableType(); try { OperateOnType(t); } finally { if (t != null) { ((IDisposable)t)

问题 This question already has an answer here: Getting “type or namespace name could not be found” but everything seems ok? 33 answers I have a C# solution with several projects in Visual Studio 2010 . One is a test project (I\'ll call it \" PrjTest \"), the other is a Windows Forms Application project (I\'ll call it \" PrjForm \"). There is also a third project referenced by PrjForm, which it is able to reference and use successfully. PrjForm references PrjTest , and PrjForm has a class with a

问题 User kokos answered the wonderful Hidden Features of C# question by mentioning the using keyword. Can you elaborate on that? What are the uses of using ? 回答1: The reason for the using statement is to ensure that the object is disposed as soon as it goes out of scope, and it doesn't require explicit code to ensure that this happens. As in Understanding the 'using' statement in C# , the C# compiler converts using (MyResource myRes = new MyResource()) { myRes.DoSomething(); } to { // Limits