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Collections.emptyMap() vs new HashMap()
...rrays or collections, not null" demonstrates returning an empty collection and perhaps even demonstrates using these emptyList(), emptySet(), and emptyMap() methods on the Collections class to get an empty collection that also has the additional benefit of being immutable. From Item #15 "Minimize ...
What does “error: option --single-version-externally-managed not recognized” indicate?
...not recognized when pip install ing varions packages (including PyObjC and astropy ). I've never seen this error before, but it's now also showing up on travis-ci builds for which nothing has changed.
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Panel.Dock Fill ignoring other Panel.Dock setting
If you create a panel on a form and set it to Dock=Top and drop another panel and set its Dock=Fill, it may fill the entire form, ignoring the first panel. Changing the tab order does nothing.
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Why do we need the “event” keyword while defining events?
I don't understand why do we need the "event" keyword while defining events, when we can do the same thing without using "event" keyword, just by using the delegates.
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Is there a “theirs” version of “git merge -s ours”?
...ork as expected.
Of course, doing the actual removal with the git rm command will prevent the conflict from happening in the first place.
Note: A longer form option also exists.
To use it, replace:
-X theirs
with:
--strategy-option=theirs
...
How to resize a VirtualBox vmdk file
I've run out of space on a virtual machine disk which is a vmdk and need to resize the virtual image. Resizing with the command
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SQL how to make null values come last when sorting ascending
...e with a datetime field. The field in question can be null. I have a query and I want the results sorted ascendingly by the datetime field, however I want rows where the datetime field is null at the end of the list, not at the beginning.
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What does “=>” mean in PHP?
...the context of that foreach loop, it assigns the key of the array to $user and the value to $pass.
Example:
$user_list = array(
'dave' => 'apassword',
'steve' => 'secr3t'
);
foreach ($user_list as $user => $pass) {
echo "{$user}'s pass is: {$pass}\n";
}
// Prints:
// "dave's...
Covariance and contravariance real world example
I'm having a little trouble understanding how I would use covariance and contravariance in the real world.
9 Answers
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How to properly create composite primary keys - MYSQL
... gross oversimplification of an intense setup I am working with. table_1 and table_2 both have auto-increment surrogate primary keys as the ID. info is a table that contains information about both table_1 and table_2 .
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