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What does the Java assert keyword do, and when should it be used?
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Assertions (by way of the assert keyword) were added in Java 1.4. They are used to verify the correctness of an invariant in the code. They should never be triggered in production code, and are indicative of a bug or misuse of a code p...
How to split a large text file into smaller files with equal number of lines?
I've got a large (by number of lines) plain text file that I'd like to split into smaller files, also by number of lines. So if my file has around 2M lines, I'd like to split it up into 10 files that contain 200k lines, or 100 files that contain 20k lines (plus one file with the remainder; being ev...
Can't escape the backslash with regex?
...ex("\\\\")
is interpreted as...
regex("\\" [escaped backslash] followed by "\\" [escaped backslash])
is interpreted as...
regex(\\)
is interpreted as a regex that matches a single backslash.
Depending on the language, you might be able to use a different form of quoting that doesn't parse...
Is iterating ConcurrentHashMap values thread safe?
...t each iterator you obtain from a ConcurrentHashMap is designed to be used by a single thread and should not be passed around. This includes the syntactic sugar that the for-each loop provides.
What happens if I try to iterate the map with two threads at the same time?
It will work as expected...
Why are variables “i” and “j” used for counters?
...a formal sum like this can be construed as degrees of freedom [directions, by another name] of the equation.
– David
Dec 5 '10 at 19:57
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How to sort the result from string_agg()
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With postgres 9.0+ you can write:
select string_agg(product,' | ' order by product) from "tblproducts"
Details here.
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When to use a View instead of a Table?
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Views for insertion/updates:
You can handle security issues with views by using such functionality as Oracle's "WITH CHECK OPTION" clause directly in the view
Drawbacks
You lose information about relations (primary keys, foreign keys)
It's not obvious whether you will be able to insert/updat...
What are the differences between “generic” types in C++ and Java?
... new foreach construct.
EDIT: the opinion above on usefulness was written by a younger self. Java's generics help with type-safety of course.
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What does mvn install in maven exactly do
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As you might be aware of, Maven is a build automation tool provided by Apache which does more than dependency management. We can make it as a peer of Ant and Makefile which downloads all of the dependencies required.
On a mvn install, it frames a dependency tree based on the project configur...
The relationship could not be changed because one or more of the foreign-key properties is non-nulla
I am getting this error when I GetById() on an entity and then set the collection of child entities to my new list which comes from the MVC view.
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