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How to get milliseconds from LocalDateTime in Java 8
...eady have a LocalDateTime or similar object from somewhere and you want to convert it to milliseconds since the epoch. It's not possible to do that directly, since the LocalDateTime family of objects has no notion of what time zone they're in. Thus time zone information needs to be supplied to find ...
Should try…catch go inside or outside a loop?
...ly no performance difference in where the try/catch structures are placed. Internally, they are implemented as a code-range table in a structure that is created when the method is called. While the method is executing, the try/catch structures are completely out of the picture unless a throw occurs,...
BSS段、数据段、代码段、堆与栈 剖析 - C/C++ - 清泛网 - 专注C/C++及内核技术
...区。
【例一】
用cl 编译两个小程序如下：
程序1:
int ar[30000];
void main()
{
......
}
程序2:
int ar[300000] = {1, 2, 3, 4, 5, 6 };
void main()
{
......
}
发现程序2 编译之后所得的.exe 文件比程序1 的要大得多。当下甚为不解，于...
Returning unique_ptr from functions
...the object were designated by an rvalue.
Just wanted to add one more point that returning by value should be the default choice here because a named value in the return statement in the worst case, i.e. without elisions in C++11, C++14 and C++17 is treated as an rvalue. So for example the follo...
Will using goto leak variables?
...abels).
1. Label scope
You can't jump across functions:
void f() {
int x = 0;
goto lol;
}
int main() {
f();
lol:
return 0;
}
// error: label 'lol' used but not defined
[n3290: 6.1/1]: [..] The scope of a label is the function in which
it appears. [..]
2. Object initiali...
What is a “context bound” in Scala?
... to Scala 2.7, tabulate could be
written as follows:
def tabulate[T](len: Int, f: Int => T) = {
val xs = new Array[T](len)
for (i <- 0 until len) xs(i) = f(i)
xs
}
In Scala 2.8 this is no longer possible, because runtime information is necessary to create the right representatio...
Quicksort vs heapsort
...hough there remains
the chance of worst case performance
except in the introsort variant, which
switches to heapsort when a bad case
is detected. If it is known in advance
that heapsort is going to be
necessary, using it directly will be
faster than waiting for introsort to
switch to...
C++ Double Address Operator? (&&)
...
&& is new in C++11. int&& a means "a" is an r-value reference. && is normally only used to declare a parameter of a function. And it only takes a r-value expression. If you don't know what an r-value is, the simple explanation is...
How to rethrow the same exception in SQL Server
...nd try
begin catch
declare @ErrorMessage nvarchar(max), @ErrorSeverity int, @ErrorState int;
select @ErrorMessage = ERROR_MESSAGE() + ' Line ' + cast(ERROR_LINE() as nvarchar(5)), @ErrorSeverity = ERROR_SEVERITY(), @ErrorState = ERROR_STATE();
if @@trancount > 0 rollback transaction;
...
What is size_t in C?
...a:
According to the 1999 ISO C standard
(C99), size_t is an unsigned integer
type of at least 16 bit (see sections
7.17 and 7.18.3).
size_tis an unsigned data type
defined by several C/C++ standards,
e.g. the C99 ISO/IEC 9899 standard,
that is defined in stddef.h.1 It can
be f...