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ConcurrentHashMap vs Synchronized HashMap
...ock.
Locking the entire collection is a performance overhead. While one thread holds on to the lock, no other thread can use the collection.
ConcurrentHashMap was introduced in JDK 5.
There is no locking at the object level,The locking is at a much finer granularity. For a ConcurrentHashMap, the...
Running multiple commands with xargs
...apply shell-like (but not quite shell-compatible) parsing to the stream it reads. (If you don't have GNU xargs, you can use tr '\n' '\0' <a.txt | xargs -0 ... to get line-oriented reading without -d).
The _ is a placeholder for $0, such that other data values added by xargs become $1 and onward, ...
Fast way to get image dimensions (not filesize)
...oo long to get the size with ImageMagick's identify because it obviously reads the images as a whole first.
8 Answers
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Is it possible to get the iOS 5.1 SDK for Xcode 4.2 on Snow Leopard?
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... and your Xcode will not be able to build to your device if you have already updated it to 5.1 because it won't be on that version of Xcode's approved SDKs
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What happens if you don't commit a transaction to a database (say, SQL Server)?
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I'm pretty sure what data is able to be read by a connection is definitely dependant on the isolation level. If you have the isolation set to READ UNCOMMITTED you can read data not yet committed and may in fact be rolled back at some point the track, but this ensur...
Accessing inactive union member and undefined behavior?
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6.5.2.3 Structure and union members
95) If the member used to read the contents of a union object is not the same as the member last used to
store a value in the object, the appropriate part of the object representation of the value is reinterpreted
as an object representation in th...
Python Script execute commands in Terminal
I read this somewhere a while ago but cant seem to find it. I am trying to find a command that will execute commands in the terminal and then output the result.
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onchange event on input type=range is not triggering in firefox while dragging
...his.value)" onchange="showVal(this.value)">
Check out this Bugzilla thread for more information.
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ipython reads wrong python version
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This is an old thread, but I've also come accross virtualenvs and like them nice for developing products. For the purpose of "everyday" analysis however, I'd rather just have a straight up usable version of python/ipython in my system.
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Retrieve version from maven pom.xml in code
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The answer below using the MavenXppReader to get the actual model is really useful, as it doesn't need to run anything to find the value. In cases where you need to know the version before anything is run, look at the answers below; it was very helpful for me...