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Does Java have a complete enum for HTTP response codes?

... I don't think there's one that's complete in the standard Java classes; HttpURLConnection is missing quite a few codes, like HTTP 100/Continue. There's a complete list in the Apache HttpComponents, though: org.apache.http.HttpStatus (replaced o...
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What is the difference between ArrayList.clear() and ArrayList.removeAll()?

... The source is strong in this one. (To all other answers: Use the source, Luke.) Notice how clear() could be implemented as just the one line, size=0; but garbage-collection wouldn't know to collect the elements in the unreachable portions of the array...
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Automatic Retina images for web sites

... Also, no double loading is a huge boon. This means you never waste anyone's bandwidth. – andrewb Apr 18 '16 at 3:05 ...
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Collections.emptyMap() vs new HashMap()

... +1 for the Effective Java reference. One nit: I would recommend parameterizing Set and HashSet in your examples, since the whole point of the emptySet() method and friends (as opposed to the constants Collections.EMPTY_SET etc.) is that they play nicely with gen...
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Android adb “Unable to open sync connection!”

I can run and debug my Android app on my phone just fine, most of the time. Then, seemingly randomly, when I try to run or debug my app from Eclipse, the Console in Eclipse says: ...
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What is Type-safe?

...me simple examples: // Fails, Trying to put an integer in a string String one = 1; // Also fails. int foo = "bar"; This also applies to method arguments, since you are passing explicit types to them: int AddTwoNumbers(int a, int b) { return a + b; } If I tried to call that using: int Sum ...
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How to determine if a list of polygon points are in clockwise order?

...l in the case of a non-convex polygon, such as a crescent. Here's a simple one that will work with non-convex polygons (it'll even work with a self-intersecting polygon like a figure-eight, telling you whether it's mostly clockwise). Sum over the edges, (x2 − x1)(y2 + y1). If the result is positi...
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How do I convert an interval into a number of hours with postgres?

...s interval, and extract result is integer, not float). So. Autocast/Floor done. – Offenso Aug 12 '15 at 13:24 19 ...
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Why use a prime number in hashCode?

... inserted into will only be determined by the least significant entry (the one not multiplied at all). Similar entries will collide. Not good for a hash function. 31 is a large enough prime that the number of buckets is unlikely to be divisible by it (and in fact, modern java HashMap implementation...
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How do you Force Garbage Collection from the Shell?

... I've used popen2 in Python or open3 in Perl to do this. UPDATE: here's a one-liner using jmxterm: echo run -b java.lang:type=Memory gc | java -jar jmxterm-1.0-alpha-4-uber.jar -n -l host:port share | ...