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What is an efficient way to implement a singleton pattern in Java? [closed]

...erializable Singleton public enum Elvis { INSTANCE; private final String[] favoriteSongs = { "Hound Dog", "Heartbreak Hotel" }; public void printFavorites() { System.out.println(Arrays.toString(favoriteSongs)); } } Edit: An online portion of "Effective Java" says:...
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What is the meaning of single and double underscore before an object name?

...n is meant to call, not you. Let's take a look: >>> name = "test string" >>> name.__len__() 11 >>> len(name) 11 >>> number = 10 >>> number.__add__(40) 50 >>> number + 50 60 There is always an operator or native function which calls these magi...
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When should I use mmap for file access?

...that you do not access outside of the map. It can easily happen if you use string functions on your map, and your file does not contain a \0 at the end. It will work most of the time when your file size is not a multiple of the page size as the last page is filled with 0 (the mapped area is always i...
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How do you write a migration to rename an ActiveRecord model and its table in Rails?

...wercase, and even UPPERCASE (which may occur in comments) versions of your strings. It's best to search for plural versions first, then singular. That way if you have an irregular plural - such as in my merchants :: businesses example - you can get all the irregular plurals correct. Otherwise you ma...
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Python : List of dict, if exists increment a dict value, if not append a new dict

...store the visited urls as a LIST? If you sort it as a dict, indexed by url string, for example, it would be way cleaner: urls = {'http://www.google.fr/': dict(url='http://www.google.fr/', nbr=1)} for url in list_of_urls: if url in urls: urls[url]['nbr'] += 1 else: urls[url]...
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What is Rack middleware?

...of them will do. Let's create a simple web application that returns a JSON string. For this we'll create a file called config.ru. The config.ru will automatically be called by the rack gem's command rackup which will simply run the contents of the config.ru in a rack-compliant webserver. So let's ad...
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catch all unhandled exceptions in ASP.NET Web Api

...ntext) { Trace.TraceError(context.ExceptionContext.Exception.ToString()); } } Then register with your application's HttpConfiguration, inside a config callback like so: config.Services.Add(typeof(IExceptionLogger), new TraceExceptionLogger()); or directly: GlobalConfiguration.C...
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What happens to a declared, uninitialized variable in C? Does it have a value?

... x86-64 calling conventions: %rdi is the first printf argument, thus the string "%d\n" at address 0x4005e4 %rsi is the second printf argument, thus i. It comes from -0x4(%rbp), which is the first 4-byte local variable. At this point, rbp is in the first page of the stack has been allocated by th...
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Create a custom event in Java

...intln("Hello there..."); } } class Test { public static void main(String[] args) { Initiater initiater = new Initiater(); Responder responder = new Responder(); initiater.addListener(responder); initiater.sayHello(); // Prints "Hello!!!" and "Hello there.....
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Do NSUserDefaults persist through an Update to an app in the Appstore?

...a, NSUserDefaults is the best way to save data such as preferences, dates, strings etc. If you are looking to save images and files, the file system is a better bet. share | improve this answer ...