它们是应用程序中用于全局对象的一种常见模式，如数据库连接和配置设置。
They are a common pattern used for global objects in an application, such as database connections and configuration Settings.
它们是应用程序中用于全局对象的一种常见模式，如数据库连接和配置设置。
They are a common pattern used for global objects in an application, such as database connections and configuration Settings.
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