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What is a NullPointerException, and how do I fix it?
What are Null Pointer Exceptions ( java.lang.NullPointerException ) and what causes them?
12 Answers
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Adb Devices can't find my phone [closed]
...ying to get adb to see my Samsung Fascinate phone so that I can install my Android apps via usb to the phone. I am using osx 10.6.7.
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Warn user before leaving web page with unsaved changes
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Short, wrong answer:
You can do this by handling the beforeunload event and returning a non-null string:
window.addEventListener("beforeunload", function (e) {
var confirmationMessage = 'It looks like you have been editing something. '
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What is a race condition?
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A race condition occurs when two or more threads can access shared data and they try to change it at the same time. Because the thread scheduling algorithm can swap between threads at any time, you don't know the order in which the threads will attempt to access the shared data. Therefore, the re...
Why is there huge performance hit in 2048x2048 versus 2047x2047 array multiplication?
...L is always power of 2.
The six comes from fact that 2^6 == 64 bytes is standard size of cache line.
Now what does this mean? Well it means that if I have address X and address Y and
(X >> 6) - (Y >> 6) is divisible by L (i.e. some large power of 2), they will be stored in the same ca...
Combining node.js and Python
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For communication between node.js and Python server, I would use Unix sockets if both processes run on the same server and TCP/IP sockets otherwise. For marshaling protocol I would take JSON or protocol buffer. If threaded Python shows up to be a bottleneck, ...
Step-by-step debugging with IPython
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You can use IPython's %pdb magic. Just call %pdb in IPython and when an error occurs, you're automatically dropped to ipdb. While you don't have the stepping immediately, you're in ipdb afterwards.
This makes debugging individual functions easy, as you can just load a file with %load...
What's the deal with a leading underscore in PHP class methods?
...of Object Oriented PHP (PHP 4). That implementation of OO was pretty bad, and didn't include things like private methods. To compensate, PHP developers prefaced methods that were intended to be private with an underscore. In some older classes you'll see /**private*/ __foo() { to give it some ext...
Java HashMap performance optimization / alternative
...or every object:
public int hashCode() {
// assume that both a and b are sorted
return a[0] + powerOf52(a[1], 1) + powerOf52(b[0], 2) + powerOf52(b[1], 3) + powerOf52(b[2], 4);
}
public static int powerOf52(byte b, int power) {
int result = b;
for (int i = 0; i < p...
Why doesn't Python have a sign function?
I can't understand why Python doesn't have a sign function. It has an abs builtin (which I consider sign 's sister), but no sign .
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