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What is copy-on-write?
I would like to know what copy-on-write is and what it is used for? The term 'copy-on-write array' is mentioned several times in the Sun JDK tutorials but I didn't understand what it meant.
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Create singleton using GCD's dispatch_once in Objective-C
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This is a perfectly acceptable and thread-safe way to create an instance of your class. It may not technically be a "singleton" (in that there can only ever be 1 of these objects), but as long as you only use the [Foo sharedFoo] method to access the objec...
ssh: connect to host github.com port 22: Connection timed out
I am under a proxy and I am pushing in to git successfully for quite a while.
Now I am not able to push into git all of a sudden.
I have set the RSA key and the proxy and double checked them, with no avail and git is throwing me the error shown in the title of the page.
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Does JavaScript have the interface type (such as Java's 'interface')?
...ect with the proper methods, which would make it conform to the interface, and then undefine all the stuff that made it conform. It'd be so easy to subvert the type system -- even accidentally! -- that it wouldn't be worth it to try and make a type system in the first place.
Instead, JavaScript us...
Dynamically select data frame columns using $ and a character value
I have a vector of different column names and I want to be able to loop over each of them to extract that column from a data.frame. For example, consider the data set mtcars and some variable names stored in a character vector cols . When I try to select a variable from mtcars using a dynamic s...
搭建高可用mongodb集群（二）—— 副本集 - 大数据 & AI - 清泛网 - 专注C/...
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Sun Dec 29 20:26:13.842 [conn3] replSet replSetInitiate admin command received from client
Sun Dec 29 20:26:13.842 [conn3] replSet replSetInitiate config object parses ok, 3 members specified
Sun Dec 29 20:26:13.847 [conn3] replSet replSetInitiate all members seem up
Sun Dec 29 20:26:13....
How to read the output from git diff?
The man page for git-diff is rather long, and explains many cases which don't seem to be necessary for a beginner. For example:
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apache to tomcat: mod_jk vs mod_proxy
What are the advantages and disadvantages of using mod_jk and mod_proxy for fronting a tomcat instance with apache?
3 A...
In which order do CSS stylesheets override?
... more general ones. Specificity is defined based on how many IDs, classes, and element names are involved, as well as whether the !important declaration was used. When multiple rules of the same "specificity level" exist, whichever one appears last wins.
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What is the difference between compile code and executable code?
I always use the terms compile and build interchangeably.
6 Answers
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