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When should we use mutex and when should we use semaphore
...p till some other thread tells you to wake up. Semaphore 'down' happens in one thread (producer) and semaphore 'up' (for same semaphore) happens in another thread (consumer)
e.g.: In producer-consumer problem, producer wants to sleep till at least one buffer slot is empty - only the consumer thread ...
What are MVP and MVC and what is the difference?
...through an interface. This is to allow mocking of the View in a unit test. One common attribute of MVP is that there has to be a lot of two-way dispatching. For example, when someone clicks the "Save" button, the event handler delegates to the Presenter's "OnSave" method. Once the save is completed,...
Changing Java Date one hour back
...e current time.
cal.setTime(currentDate);
cal.add(Calendar.HOUR, -1);
Date oneHourBack = cal.getTime();
java.util.Date
new Date(System.currentTimeMillis() - 3600 * 1000);
org.joda.time.LocalDateTime
new LocalDateTime().minusHours(1)
Java 8: java.time.LocalDateTime
LocalDateTime.now().minusH...
Is it fine to have foreign key as primary key?
...) to act as the primary key.
The only exception to this are tables with a one-to-one relationship, where the foreign key and primary key of the linked table are one and the same.
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FFmpeg: How to split video efficiently?
....ts -vcodec copy -acodec copy -ss 00:30:00 -t 01:00:00 -sn test2.mkv
echo "One command"
time ffmpeg -v quiet -y -i input.ts -vcodec copy -acodec copy -ss 00:00:00 -t 00:30:00 \
-sn test3.mkv -vcodec copy -acodec copy -ss 00:30:00 -t 01:00:00 -sn test4.mkv
Which outputs...
Two commands
real 0m...
What's the difference between belongs_to and has_one?
What is the difference between a belongs_to and a has_one ?
5 Answers
5
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What is the difference between id and class in CSS, and when should I use them? [duplicate]
...s are useful when you have, or possibly will have in the future, more than one element that shares the same style. An example may be a div of "comments" or a certain list style to use for related links.
Additionally, a given element can have more than one class associated with it, while an element...
MySQL INNER JOIN select only one row from second table
...I think that my answer is more simple and is faster because I'm using just one inner join. Maybe I'm wrong?
– Mihai Matei
Sep 21 '12 at 8:01
2
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How can I pair socks from a pile efficiently?
...as doing it is not very efficient. I was doing a naive search — picking one sock and "iterating" the pile in order to find its pair. This requires iterating over n/2 * n/4 = n 2 /8 socks on average.
...
O(nlogn) Algorithm - Find three evenly spaced ones within binary string
...cisely the number of pairs (a,c) in L such that a+c=2b. [CLRS, Ex. 30.1-7] One such pair is (b,b) always (so the coefficient is at least 1), but if there exists any other pair (a,c), then the coefficient is at least 3, from (a,c) and (c,a). For the example above, we have the coefficient of x10 to be...