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What is the difference between a.getClass() and A.class in Java?
...
time (getClass()) :23506 ns
time (.class):23838 ns
And switching the order of the calls will even result in getClass() being faster.
import java.util.LinkedHashMap;
public class PerfomanceClass {
public static void main(String[] args) {
long time2 = System.nanoTime();
Class class2 =...
Disabling swap files creation in vim
...
You can set backupdir and directory to null in order to completely disable your swap files, but it is generally recommended to simply put them in a centralized directory. Vim takes care of making sure that there aren't name collissions or anything like that; so, this is a...
When and why are database joins expensive?
... bulk disk reads which are the most expensive aspect of the exercise by an order of magnitude. Performing a join, by contrast, logically requires retrieval of only the keys. In practice, not even the key values are fetched: the key hash values are used for join comparisons, mitigating the cost of mu...
oracle group 取每组第一条 - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
...CT * FROM(
SELECT z.type , z.code ,ROW_NUMBER()
OVER(PARTITION BY z.type ORDER BY z.code) AS code_id
FROM group_info z
)
WHERE code_id =1;
这里涉及到的over()是oracle的分析函数。
参考sql reference文档：
Analytic functions compute an aggregate value based on a group of ...
Where to put include statements, header or source?
...fic requirements that you #include a certain set of headers (in a specific order). Some extremely traditional C programmers still follow this model (religiously, in at least some cases).
More recently, there's a movement toward making most headers standalone. If that header requires something else,...
The order of keys in dictionaries
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You could use OrderedDict (requires Python 2.7) or higher.
Also, note that OrderedDict({'a': 1, 'b':2, 'c':3}) won't work since the dict you create with {...} has already forgotten the order of the elements. Instead, you want to use Order...
How does the Comma Operator work
... guaranteed to have its three subexpressions (a+b, c() and d) evaluated in order. This is significant if they have side-effects. Normally compilers are allowed to evaluate subexpressions in whatever order they find fit; for example, in a function call:
someFunc(arg1, arg2, arg3)
arguments can be ...
How can I get form data with JavaScript/jQuery?
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Please also beware that in order to record a value from any form input, the input must have a name attribute.
– Chris - Jr
Oct 27 '17 at 19:37
...
Load view from an external xib file in storyboard
...ther than the original class. It doesn't actually have to be a subclass in order for this to work, but making it a subclass is what allows IB to see any IBInspectable/IBOutlet properties.
This extra boilerplate might seem suboptimal—and in a sense it is, because ideally UIStoryboard would handle ...
How do I disable the 'Debug / Close Application' dialog on Windows Vista?
...he entire system. I've found that a combination of functions are needed in order to suppress these errors, such as catching unhandled exceptions, suppressing run time checks (such as the validity of the stack pointer) and the error mode flags. This is what I've used with some success:
#include <...