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With lazy initialization, the object is first set to null. Whenever the object is requested, the object is checked, and if it is null, the object is then immediately created and returned. For example, lazy loading for a widget can be implemented in the C# programming language as such:
This example is in Smalltalk, of a typical accessor method to return the value of a variable using lazy initialization. height ^ height ifNil: [ height := 2.0 ] . The 'non-lazy' alternative is to use an initialization method that is run when the object is created and then use a simpler accessor method to fetch the value.
The implementation of the idiom relies on the initialization phase of execution within the Java Virtual Machine (JVM) as specified by the Java Language Specification (JLS). [3] When the class Something is loaded by the JVM, the class goes through initialization. Since the class does not have any static variables to initialize, the ...
A singleton implementation may use lazy initialization in which the instance is created when the static method is first invoked. In multithreaded programs, this can cause race conditions that result in the creation of multiple instances. The following Java 5+ example [6] is a thread-safe implementation, using lazy initialization with double ...
Lazy evaluation can also lead to reduction in memory footprint, since values are created when needed. [19] In practice, lazy evaluation may cause significant performance issues compared to eager evaluation. For example, on modern computer architectures, delaying a computation and performing it later is slower than performing it immediately.
Hibernate can be configured to lazy load associated collections. [2]: 289–293 Lazy loading is the default as of Hibernate 3. Related objects can be configured to cascade operations from one object to the other. For example, a parent Album class object can be configured to cascade its save and delete operations to its child Track class objects.
Until Java 1.2. the garbage collector could unload a class whenever it felt it needed the space, independent of which class loader was used to load the class. Starting with Java 1.2 classes loaded via the system classloader were never unloaded and classes loaded via other classloaders only when this other classloader was unloaded.
An example for an application that may make use of AMI is a web browser that needs to display a web page even before all images are loaded. Since method is a special case of procedure , asynchronous method invocation is a special case of asynchronous procedure call .