casting

问题 This question already has answers here : printf %f with only 2 numbers after the decimal point? (8 answers) Closed 3 months ago . This line results in double value 3.33333333335 System.out.println("Average marks of " + name + " = " + (double)sum/3); Is it possible to set a width of precision? 回答1: You can use DecimalFormat or BigDecimal as follows: import java.math.BigDecimal; import java.math.RoundingMode; import java.text.DecimalFormat; public class Main { public static void main(String[]

问题 It appears to be widely-held that type punning via reinterpret_cast is somehow prohibited (properly: "undefined behavior", that is, "behavior for which this International Standard imposes no requirements", with an explicit note that implementations may define behavior) in C++. Am I incorrect in using the following reasoning to disagree, and if so, why ? [expr.reinterpret.cast]/11 states: A glvalue expression of type T1 can be cast to the type “reference to T2 ” if an expression of type

问题 I have a database table Transaction (transactionID, LocalAmount...). where datatype for Localamount property is float . ON the UI I am trying to return a SUM of column (Localamount) in one row on a button click event. I have used decimal instead of float However I am getting an error on the code where I am casting to decimal System.NotSupportedException was unhandled by user code Message=Casting to Decimal is not supported in LINQ to Entities queries, because the required precision and scale

问题 What I want: To add a network namespace option to execsnoop bcc tool to trace only the logs with specified network namespace just like we have filter PID option in many other bcc tools. For eg: execsnoop -N "ns_id" I am using linux kernel structures to retrieve namespace id net = task->nsproxy->net_ns; and need to assign the retrieved ns to data.netns which is u32 int. What I am doing: int syscall__execve(struct pt_regs *ctx, const char __user *filename, const char __user *const __user *_

问题 I am trying to get rid of Rule 11.3 from my code. Sample code: static int32_t do_test(const char *cp) { const char *c = cp; const int32_t *x; x = (const int32_t *)cp; return *x; } I want the value of *c and *x to be same. Even-though the code is compiling and giving the correct value, "x = (int32_t *)cp;" causing violation of 11.3 and 11.8 Rule 11.3 violation: An object with pointer type shall not be converted to a pointer to a different object type. I have tried with void pointer, but the

问题 I have an abstract class Event and a concrete subclass that extends it called PlaceChangeEvent . Inside an event listener, I have the following code: void onEvent(Event event) { PlaceChangeEvent pce = null; if(event is PlaceChangeEvent) pce = (PlaceChangeEvent)event; // <== error is here else throw new Exception("Event is not a PlaceChangeEvent."); Place place = pce.place; presenterProvider.display(place); } So if the runtime type of event is PlaceChangeEvent , then I need to cast the event

问题 I have an abstract class Event and a concrete subclass that extends it called PlaceChangeEvent . Inside an event listener, I have the following code: void onEvent(Event event) { PlaceChangeEvent pce = null; if(event is PlaceChangeEvent) pce = (PlaceChangeEvent)event; // <== error is here else throw new Exception("Event is not a PlaceChangeEvent."); Place place = pce.place; presenterProvider.display(place); } So if the runtime type of event is PlaceChangeEvent , then I need to cast the event

问题 Is there a particular reason why this results in runtime exception instead of compile-time error in Java? Object[] objects = new Object[10]; String[] strings = (String[])objects; 回答1: The check has to be done at run time because of this case: public class Test { public static void main(String[] args){ String[] stringsBase = {"aaa", "bbb", "ccc"}; Object[] objects = stringsBase; String[] strings = (String[])objects; System.out.println(strings[1]); } } This is a valid, working program. Without

问题 Is there a particular reason why this results in runtime exception instead of compile-time error in Java? Object[] objects = new Object[10]; String[] strings = (String[])objects; 回答1: The check has to be done at run time because of this case: public class Test { public static void main(String[] args){ String[] stringsBase = {"aaa", "bbb", "ccc"}; Object[] objects = stringsBase; String[] strings = (String[])objects; System.out.println(strings[1]); } } This is a valid, working program. Without

问题 Is there a particular reason why this results in runtime exception instead of compile-time error in Java? Object[] objects = new Object[10]; String[] strings = (String[])objects; 回答1: The check has to be done at run time because of this case: public class Test { public static void main(String[] args){ String[] stringsBase = {"aaa", "bbb", "ccc"}; Object[] objects = stringsBase; String[] strings = (String[])objects; System.out.println(strings[1]); } } This is a valid, working program. Without