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Why does Java's hashCode() in String use 31 as a multiplier?

...to Joshua Bloch's Effective Java (a book that can't be recommended enough, and which I bought thanks to continual mentions on stackoverflow): The value 31 was chosen because it is an odd prime. If it were even and the multiplication overflowed, information would be lost, as multiplication by 2 i...
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How can I do DNS lookups in Python, including referring to /etc/hosts?

...for the late comment: the result may be cached by the local resolver. nscd and nslcd on Unix boxes can do this. It could also be cached by a local name server configured for caching (a common setup, once upon a time. Probably not so much now). It's not a straightforward ‘no’ answer, unfortunatel...
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When does invoking a member function on a null instance result in undefined behavior?

... Both (a) and (b) result in undefined behavior. It's always undefined behavior to call a member function through a null pointer. If the function is static, it's technically undefined as well, but there's some dispute. The first thin...
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What is meant by Scala's path-dependent types?

.... It's something to do with inner-classes but what does this actually mean and why do I care? 1 Answer ...
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Connecting to Azure website via FTP

...ve you seen this answer? are you using the full credentials including site and a proper ftp client? – Simon Opelt Mar 15 '14 at 22:53 7 ...
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Differences in auto-unboxing between Java 6 vs Java 7

I have noted a difference in auto unboxing behavior between Java SE 6 and Java SE 7. I'm wondering why that is, because I can't find any documentation of changes in this behavior between these two versions. ...
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Swapping two variable value without using third variable

... *x ^= *y; } } Why the test? The test is to ensure that x and y have different memory locations (rather than different values). This is because (p xor p) = 0 and if both x and y share the same memory location, when one is set to 0, both are set to 0. When both *x and *y are 0, all o...
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How do I test for an empty string in a Bash case statement?

... The case statement uses globs, not regexes, and insists on exact matches. So the empty string is written, as usual, as "" or '': case "$command" in "") do_empty ;; something) do_something ;; prefix*) do_prefix ;; *) do_other ;; esac ...
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When to use cla(), clf() or close() for clearing a plot in matplotlib?

... of many axes. Additionally, there are functions from the pyplot interface and there are methods on the Figure class. I will discuss both cases below. pyplot interface pyplot is a module that collects a couple of functions that allow matplotlib to be used in a functional manner. I here assume that...
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Is there a difference between /\s/g and /\s+/g?

... \s means "one space", and \s+ means "one or more spaces". But, because you're using the /g flag (replace all occurrences) and replacing with the empty string, your two expressions have the same effect. ...