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Any call to a class (static or constructor call), triggers the static constructor execution. Static constructors are thread safe and implement a singleton pattern. When used in a generic programming class, static constructors are called at every new generic instantiation one per type. [8]: 38 [4]: 111 Static variables are instantiated as well.
The static class definition LazyHolder within it is not initialized until the JVM determines that LazyHolder must be executed. The static class LazyHolder is only executed when the static method getInstance is invoked on the class Something , and the first time this happens the JVM will load and initialize the LazyHolder class.
In computer programming, lazy initialization is the tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed.
Before a class derived from an abstract class can be instantiated, all abstract methods of its parent classes must be implemented by some class in the derivation chain. [ 25 ] Most object-oriented programming languages allow the programmer to specify which classes are considered abstract and will not allow these to be instantiated.
static is a reserved word in many programming languages to modify a declaration. The effect of the keyword varies depending on the details of the specific programming language, most commonly used to modify the lifetime (as a static variable) and visibility (depending on linkage), or to specify a class member instead of an instance member in classes.
For example, class UnicodeConversionMixin might provide a method unicode_to_ascii() when included in class FileReader and class WebPageScraper, which do not share a common parent. Abstract classes cannot be instantiated into objects; they exist only for inheritance into other "concrete" classes that can be instantiated.
In computer science, an instance is an occurrence of a software element that is based on a type definition. When created, an occurrence is said to have been instantiated, and both the creation process and the result of creation are called instantiation.
How can an object's instantiation be deferred to a subclass? Create an object by calling a factory method instead of directly calling a constructor. This enables the creation of subclasses that can change the way in which an object is created (for example, by redefining which class to instantiate).