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MongoDB: update every document on one field
I have a collected named foo hypothetically.
4 Answers
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How to avoid null checking in Java?
...ts they are participating in and defensively overcheck for nulls. Additionally, when writing their own code, they tend to rely on returning nulls to indicate something thus requiring the caller to check for nulls.
To put this another way, there are two instances where null checking comes up:
Whe...
How to get ID of the last updated row in MySQL?
...AT_WS(',', fooid, @uids) );
SELECT @uids;
This will return a string with all the IDs concatenated by a comma.
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Ways to iterate over a list in Java
...ng somewhat new to the Java language I'm trying to familiarize myself with all the ways (or at least the non-pathological ones) that one might iterate through a list (or perhaps other collections) and the advantages or disadvantages of each.
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What is recursion and when should I use it?
...sion.
To see why, walk through the steps that the above languages use to call a function:
space is carved out on the stack for the function's arguments and local variables
the function's arguments are copied into this new space
control jumps to the function
the function's code runs
the function's...
How to insert a text at the beginning of a file?
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To actually insert a new line: sed -i '1s/^/<added text> \n/' file
– jslatts
Sep 17 '13 at 13:27
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How to assign the output of a Bash command to a variable? [duplicate]
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In this specific case, note that bash has a variable called PWD that contains the current directory: $PWD is equivalent to `pwd`. (So do other shells, this is a standard feature.) So you can write your script like this:
#!/bin/bash
until [ "$PWD" = "/" ]; do
echo "$PWD"
ls ...
Difference between a virtual function and a pure virtual function [duplicate]
... class. Derived classes can override virtual functions. Virtual functions called through base class pointers/references will be resolved at run-time. That is, the dynamic type of the object is used instead of its static type:
Derived d;
Base& rb = d;
// if Base::f() is virtual and Derived o...
CSS “and” and “or”
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Are we really still concerned with supporting older versions of IE in 2018? Not even Microsoft does.
– Anomaly
Mar 15 '18 at 12:18
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Unrecognized SSL message, plaintext connection? Exception
... you. You can do the same yourself. Indeed HttpURLConnection will automatically do it for you, if you don't specify a port at all.
– Marquis of Lorne
Jun 9 '14 at 23:54
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