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Can constructors throw exceptions in Java?
...structor ought to be careful to avoid acquiring unmanaged resources (file handles etc) and then throwing an exception without releasing them. For example, if the constructor tries to open a FileInputStream and a FileOutputStream, and the first succeeds but the second fails, you should try to close t...
Check if directory mounted with bash
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Running the mount command without arguments will tell you the current mounts. From a shell script, you can check for the mount point with grep and an if-statement:
if mount | grep /mnt/md0 > /dev/null; then
echo "yay"
else
echo "nay"
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How do I initialize the base (super) class?
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Python (until version 3) supports "old-style" and new-style classes. New-style classes are derived from object and are what you are using, and invoke their base class through super(), e.g.
class X(object):
def __init__(self, x):
pass
def doit(self, bar):
pa...
Update MongoDB field using value of another field
...ion 4.2+ which allows using of aggregation pipeline in the update document and the updateOne, updateMany or update collection method. Note that the latter has been deprecated in most if not all languages drivers.
MongoDB 4.2+
Version 4.2 also introduced the $set pipeline stage operator which is an...
How do I get out of a screen without typing 'exit'?
I screen -r 'd into a django server that's running and I can't simply Ctrl-C and exit out of it.
5 Answers
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How to set host_key_checking=false in ansible inventory file?
I would like to use ansible-playbook command instead of ' vagrant provision '. However setting host_key_checking=false in the hosts file does not seem to work.
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How to check whether a variable is a class or not?
...k is redundant. If it didn't there would be no way to instantiate whatever and thus you couldn't perform the check in the first place.
– a_guest
Dec 16 '16 at 12:42
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Default initialization of std::array?
...zed (C++11 §8.5/11). That includes objects of type std::array<T, N> and T[N].
Be aware that there are types for which default initialization has no effect and leaves the object's value indeterminate: any non-class, non-array type (§8.5/6). Consequently, a default-initialized array of object...
How big can a user agent string get?
...pt, throwing 413 Entity Too Large if it exceeds.
Depending on web-server and their settings these limits vary from 4KB to 64KB (total for all headers).
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Why do we not have a virtual constructor in C++?
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Hear it from the horse's mouth. :)
From Bjarne Stroustrup's C++ Style and Technique FAQ Why don't we have virtual constructors?
A virtual call is a mechanism to get work done given partial
information. In particular, "virtual" allows us to call a function
knowing only any interfaces and...