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Difference in System. exit(0) , System.exit(-1), System.exit(1 ) in Java
...er programming languages where it's useful to know if something went wrong and what went wrong.
Exit code is
0 when execution went fine;
1, -1, whatever != 0 when some error occurred, you can use different values for different kind of errors.
If I'm correct exit codes used to be just positive n...
Why does parseInt(1/0, 19) return 18?
...parseInt scans the input "Infinity" to find which part of it can be parsed and stops after accepting the first I (because n is not a valid digit in base 19).
Therefore it behaves as if you called parseInt("I", 19), which converts to decimal 18 by the table above.
...
Does Java support default parameter values?
...
No, the structure you found is how Java handles it (that is, with overloading instead of default parameters).
For constructors, See Effective Java: Programming Language Guide's Item 1 tip (Consider static factory methods instead of constructors) if the overloading ...
Set transparent background using ImageMagick and commandline prompt
Suppose you have any image (PNG or JPG).
This image has a white background and I need to make this background transparent.
...
How would I extract a single file (or changes to a file) from a git stash?
...ed as a commit whose tree records the state of the
working directory, and its first parent is the commit at HEAD when the
stash was created.
So you can treat stash (e.g. stash@{0} is first / topmost stash) as a merge commit, and use:
$ git diff stash@{0}^1 stash@{0} -- <filename...
Creating temporary files in bash
...many shell scripts take the name of the program with
the pid as a suffix and use that as a temporary file name. This kind
of naming scheme is predictable and the race condition it creates is
easy for an attacker to win. A safer, though still inferior, approach
is to make a temporary directo...
Convert a list of data frames into one data frame
...
since it's 2018 and dplyr is both fast and a solid tool to use, I've changed this to the accepted answer. The years, they fly by!
– JD Long
Jan 12 '19 at 12:03
...
Regular expression for letters, numbers and - _
...iteral .
References
regular-expressions.info/Anchors, Character Classes and Repetition
In PHP
Here's a snippet to show how you can use this pattern:
<?php
$arr = array(
'screen123.css',
'screen-new-file.css',
'screen_new.js',
'screen new file.css'
);
foreach ($arr as $s) {
if...
Does ARC support dispatch queues?
...
The short answer: YES, ARC retains and releases dispatch queues.
And now for the long answer…
If your deployment target is lower than iOS 6.0 or Mac OS X 10.8
You need to use dispatch_retain and dispatch_release on your queue. ARC does not manage ...
Swift equivalent for MIN and MAX macros
In C / Objective-C it is possible to find the minimum and maximum value between two numbers using MIN and MAX macros. Swift doesn't support macros and it seems that there are no equivalents in the language / base library. Should one go with a custom solution, maybe based on generics like this one ?...