Nowadays there are lots of patterns, such as the singleton pattern, factory pattern, etc.
现在总结出很多模式，例如：单例模式，工厂模式等。
参考来源 - Java EE模式框架在中小企业Web实施应用中的研究
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Singleton pattern
abstract:In software engineering, the singleton pattern is a design pattern that restricts the Instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system.