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Why is Java's SimpleDateFormat not thread-safe? [duplicate]
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SimpleDateFormat stores intermediate results in instance fields. So if one instance is used by two threads they can mess each other's results.
Looking at the source code reveals that there is a Calendar instance field, which is used by operations on DateFormat / SimpleDateFormat.
For example p...
How update the _id of one MongoDB Document?
I want update an _id field of one document. I know it's not a really good pratice. But with some technical reason, I need update it. If I try to update it I get:
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Does adding a duplicate value to a HashSet/HashMap replace the previous value
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In the case of HashMap, it replaces the old value with the new one.
In the case of HashSet, the item isn't inserted.
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What is the difference between dict.items() and dict.iteritems() in Python2?
...hod named iteritems(). The original remains for backwards compatibility.
One of Python 3’s changes is that items() now return iterators, and a list is never fully built. The iteritems() method is also gone, since items() in Python 3 works like viewitems() in Python 2.7.
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In C++, what is a virtual base class?
...ual A {};
class D : public B, public C {};
This means that there is only one "instance" of A included in the hierarchy. Hence
D d;
d.Foo(); // no longer ambiguous
This is a mini summary. For more information, have a read of this and this. A good example is also available here.
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How do I dump the data of some SQLite3 tables?
..., as it should be easily re-entered into the database later and should be done from the command line. Something like
13 Ans...
Copying data from one SQLite database to another
...ing data, so I was wondering if it was possible to copy a whole table from one database to another?
8 Answers
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Insert a commit before the root commit in Git?
... newroot $commit
You can of course rearrange the whole procedure into a one-liner if you know your shell well enough.
Without plumbing
With regular porcelain commands, you cannot create an empty commit without checking out the newroot branch and updating the index and working copy repeatedly, f...
How can I create a temp file with a specific extension with .NET?
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(To quote from the wiki article on the probabilty of a collision:
...one's annual risk of being hit by a
meteorite is estimated to be one
chance in 17 billion [19], that means
the probability is about 0.00000000006
(6 × 10−11), equivalent to the odds of
creating a few tens of tril...
The multi-part identifier could not be bound
...to be aware of how to do that properly.
The thing is, explicit joins (the ones that are implemented using the JOIN keyword) take precedence over implicit ones (the 'comma' joins, where the join condition is specified in the WHERE clause).
Here's an outline of your query:
SELECT
…
FROM a, b LE...