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Questions every good Java/Java EE Developer should be able to answer? [closed]
...ing through Questions every good .Net developer should be able to answer and was highly impressed with the content and approach of this question, and so in the same spirit, I am asking this question for Java/Java EE Developer.
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Django filter queryset __in for *every* item in list
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Summary:
One option is, as suggested by jpic and sgallen in the comments, to add .filter() for each category. Each additional filter adds more joins, which should not be a problem for small set of categories.
There is the aggregation approach. This query would be short...
What is the difference between lower bound and tight bound?
...the upper bound, while Omega is the lower bound. Theta requires both Big O and Omega, so that's why it's referred to as a tight bound (it must be both the upper and lower bound).
For example, an algorithm taking Omega(n log n) takes at least n log n time, but has no upper limit. An algorithm taking...
How do arrays in C# partially implement IList?
...tation is somewhat more complicated than we might think. Both the compiler and the CLR try very hard to give the impression that an array type implements IList<T> - but array variance makes this trickier. Contrary to the answer from Hans, the array types (single-dimensional, zero-based anyway)...
Add unique constraint to combination of two columns
I have a table and, somehow, the same person got into my Person table twice. Right now, the primary key is just an autonumber but there are two other fields that exist that I want to force to be unique.
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Is there a regular expression to detect a valid regular expression?
...group start
(?:
(?:[^?+*{}()[\]\\|]+ # literals and ^, $
| \\. # escaped characters
| \[ (?: \^?\\. | \^[^\\] | [^\\^] ) # character classes
(?: [^\]\\]+ | \\. )* \]
| \( (?:\?[:=!]|\?<[=!]|\?>)? (?1)?? ...
How to design a database for User Defined Fields?
...s a variant of #2). This answer is specifically tailored to this situation and the description of the data distribution and access patterns described.
Pros:
Because you indicate that some UDFs
have values for a small portion of
the overall data set, a separate
table would give you the best
perfor...
Delete all local changesets and revert to tree
I'm using Mercurial and I've got into a terrible mess locally, with three heads. I can't push, and I just want to delete all my local changes and commits and start again with totally clean code and a clean history.
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How do I pre-populate a jQuery Datepicker textbox with today's date?
...Update: There are reports this no longer works in Chrome.
This is concise and does the job (obsolete):
$(".date-pick").datepicker('setDate', new Date());
This is less concise, utilizing chaining allows it to work in chrome (2019-06-04):
$(".date-pick").datepicker().datepicker('setDate', new Dat...
BigDecimal - to use new or valueOf
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Those are two separate questions: "What should I use for BigDecimal?" and "What do I do in general?"
For BigDecimal: this is a bit tricky, because they don't do the same thing. BigDecimal.valueOf(double) will use the canonical String representation of the double value passed in to instantiate ...