JSR 292 Goodness: lazy Singleton Pattern

The idea of the lazy Singleton Pattern is to initialize a static field only when needed and not during the initialization of the class. The code for that pattern is this one: private static Database database; public static Database getDatabase() { synchronized (DCL.class) { if (database == null) { database = new Database(); } return database; } } In that case, you pay the synchronization cost each time you access to the variable. Note that it's far from obvious that in a real application this synchronization cost is significant, but for the rest of this blog, let say that this cost is not acceptable. As you probably already know the Double-Checked Locking idiom (DCL) is broken. The recommanded idiom is to declare another class and to use natural lazy loading of the class in Java.  static class Lazy { private static final Database database = new Database(); } public static Database getDatabase() { return Lazy.database; } In this blog post, I want to show you another way to solve that problem using invokedynamic. The invokedynamic instruction has a powerful initialization mechanism, the first time an invokedynamic instruction is seen a bootstrap method (a factory method) associated to the invokedynamic instruction is called to get a method handle (a safe function pointer) that will be called for the current call and the next calls. public static Data...

Date: November, 05 2010
Url: http://www.java.net/blog/forax/archive/2010/11/04/jsr-292-goodness-singleton-pattern

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