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Regex to match a digit two or four times
...wo digits, and optionally two more
(?:\d{2}){1,2} <-- two digits, times one or two
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Maven: how to do parallel builds?
...
Maven 3 (as of beta 1) now supports parallel builds as an experimental feature.
For example,
mvn -T 4 clean install # Builds with 4 threads
mvn -T 1C clean install # 1 thread per cpu core
mvn -T 1.5C clean install # 1.5 thread per cpu core
Full documentation can be found on the Maven wik...
Aggregate function in an SQL update query?
...o set the value in one table to the sum of the values in another table. Something along these lines:
6 Answers
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What does “hashable” mean in Python?
I tried searching internet but could not find the meaning of hashable.
9 Answers
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NOT IN vs NOT EXISTS
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I always default to NOT EXISTS.
The execution plans may be the same at the moment but if either column is altered in the future to allow NULLs the NOT IN version will need to do more work (even if no NULLs are actually present in the data) and the semantics of NOT IN if NULLs are present a...
Container-fluid vs .container
...available width.
The difference between container and container-fluid comes from these lines of CSS:
@media (min-width: 568px) {
.container {
width: 550px;
}
}
@media (min-width: 992px) {
.container {
width: 970px;
}
}
@media (min-width: 1200px) {
.container {
width: 1170px...
.prop('checked',false) or .removeAttr('checked')?
With the introduction of the prop method, now I need to know the accepted way of unchecking a checkbox. Is it:
4 Answers
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What is the relative performance difference of if/else versus switch statement in Java?
...plication's performances, I am wondering which of "if/else" or switch statement is better regarding performance?
8 Answers
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Select random row from a sqlite table
... a.id = b.id WHERE b.bar = 2 ORDER BY RANDOM() LIMIT 1; I always get the same row.
– Helmut Grohne
Sep 19 '13 at 8:18
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C++ const map element access
I tried to use the operator[] access the element in a const C++ map, but this method failed. I also tried to use "at()" to do the same thing. It worked this time. However, I could not find any reference about using "at()" to access element in a const C++ map. Is "at()" a newly added function in C++ ...