casting

问题 I have column response_xml and request_xml which consist of large string. I have used substring function for this large string in order to fetch the SUBSCRIPTION_ID from response_xml and orderType from request_xml. The query is working fine. But now i want to put condition for this query such that it should only return SUBSCRIPTION_ID where orderType='NEW'. I used the below query but resulting an error as ORA-00932: inconsistent datatypes: expected - got CLOB 00932. 00000 - "inconsistent

问题 I use spring boot for my webservice. Each method returns Map<Object, Object> because it is a general type and the methods are able to return any response, either a primitive int or complex custom object of User . Also I used Map<Object, Object> to eliminate backslash "\" in JSON, instead of using String. But I got problem with variable casting in client (Android app). Number variables in Map are automatically casted to double (1.0, 2.0, 3.0, 5.0, ...) while it is long in server. If I cast

问题 class Foo { public $var ; function __construct($value) { $this->var = $value ; } } $myFoo = new Foo('hello'); echo $myFoo->var . '<br>' ; // output : hello // Question : how can I prevent another programer from accidentaly doing the following $myFoo = 4 ; echo $myFoo ; // output : 4 my question is in the comment // Question :... I would like my coworkers being able to assign values to $myFoo use only $myFoo->var (or whatever public mutators are available in the class Foo) thank you EDIT :

问题 This is just an oddity I ran into and can't quite understand what's happening. int main() { int i{ 5 }; void* v = &i; int* t = reinterpret_cast<int*>(v); int u = reinterpret_cast<int&>(v); int i2 = *t; } t is correctly 5 and u is garbage. What's going on? 回答1: v stores the address of i , which is, as you put it, garbage. (it's not really garbage, but the value itself is meaningless, except as it is the address of i in this particular run of the program). u stores the same value (bitwise) as v

问题 This question already has answers here : How do I print my Java object without getting “SomeType@2f92e0f4”? (10 answers) Closed 4 years ago . Consider a simple case like this one : public static void array() { String myString = "STACKOVERFLOW"; int [] checkVal = new int[myString.length()]; for(int i=0; i<myString.length();i++){ checkVal[i] = (int)myString.charAt(i); } System.out.println(checkVal[0]); System.out.println(checkVal[1]); System.out.println(checkVal[2]); System.out.println(checkVal

问题 Is it possible to cast a variable using a different variable instead of using the name of a class? Here is functioning code: Object five = new Integer(5); int six = (Integer) five + 1; I would love to replace that second line with int six = five + 1; but I can't, so could i do something like one of these alternatives: int six = (foo) five + 1; int six = foo(five) + 1; int six = foo.cast(five) + 1; ?? why i want to do this I have a Map with keys of a custom enum, and with values of type String

问题 I need to copy curr_task->pid , a pid_t in kernel space, to a structure's field in user space that has space for a long. Since this is a widening conversion, I'm not expecting any issues. However, I'm getting an annoying compiler warning ( copy_long_to_user is for all intents and purposes the same as copy_to_user ): cs300/process_ancestors.c:31:3: warning: passing argument 2 of ‘copy_long_to_user’ from incompatible pointer type [enabled by default] if(copy_long_to_user(&info_array[num_filled

问题 I just ran this query: UPDATE mytable SET mycol='text' WHERE mycol=0; The point being that the column mycol is a varchar , yet i treated is as an int as well. To my surprise, the where clause evaluated to true on ALL rows of the table, empty or not. So, why does a nonempty string compare equal to an integer zero? 回答1: This is very well documented behavior in MySQL. When a string is encountered in a context that calls for a number, MySQL converts the string to a number, starting with digits at

问题 This is related to JoGusto's answer at Casting Error: lvalue required as left operand of assignment. In the answer, he/she states: but there is one case where it is not true: casting, then dereferencing a pointer: *((int *) chrPtrValue) = some_integer_expression; I think I found the answer at Joseph Mansfield answer from Why does an lvalue cast work?, where he cited the standard. But that confused me more because I can differentiate between lvalues and rvalues , but xvalues and prvalues are

问题 I can't share my code bu basically i have a class implementing interface like so: public interface A { void doA(); } public class B: A { public void doA() { // Doing A } } and i have a list of A like so: List<B> list = new List<B>(); list.Add(new B()); now i want an IEnumerable<A> . so i tried these 3 lines: List<A> listCast = (List<A>)list; IEnumerable<A> listCastToEnumerable = (IEnumerable<A>)list; IEnumerable<A> listCastExt = list.Cast<A>(); The first one got an error: "Error 1 Cannot