单例模式可能是最常用的OOP设计模式之一了；它限制了一个类的对象实例数只能为1。
The singleton pattern is probably one of the most often used OOP design patterns; it restricts the number of object instances of a class to one.
单例模式是一种非常有用的设计模式，它允许你的类对外只提供一个实例，但是常犯的错误在于不止一个实例被创建。
The singleton is a useful design pattern for allowing only one instance of your class, but common mistakes can inadvertently allow more than one instance to be created.
单例模式是一种有用的控制类访问的途径，他能保证只有一个类实例存在。
Singletons are a useful way to control access to a class, making sure that only one instance can exist.
比如数据库连接池就是单例设计模式的一个例子：我们一般不想让应用程序具有连接池类的多个资源密集型实例。
An example use case for a singleton would be a database connection pool: you don't want your application to have multiple resource-intensive instances of a connection pool class.
最后，在单例模式的一些实现方式中，单例类的子类能够动态地重载方法，这是静态方法所不能办到的。
With some implementations of the singleton, you allow writers of subclasses to override methods polymorphically, something not possible with static methods.
这是一个可用来创建单例类实例确不需要为每个特定的类重写单例模式代码的可重用的类。
This is a class that can be used repeatedly to instantiate a class as a singleton without having to re-write the singleton pattern code for that specific class.
这样分离出单例结构的代码，将有利于保持按单例模式使用类或不按单例模式使用类的灵活性。
This has the added benefit of separating singleton code from the class code leaving the flexibility to use several instances of the class or using the class as a singleton.
尽管单例实现使用的是子类的类名，其他的模式（比如稍后介绍的活动记录模式）需要引用其他的静态属性。
Whereas the singleton implementation uses the subclass's class name, other patterns (such as active record, covered later) need to reference other static properties.
同时，如果使用创建单实例的方法实现单例模式，单例类还具有创建多个实例的变通能力。
Likewise, with a singleton implemented as single instance, you leave open the possibility of altering the class to create more instances in the future.
单例模式：确保一个类只有一个实例，并提供一个全局访问点。
The Singleton Pattern:ensures a class has only on instance, and provides a global point of access to it.
使用类来实现单例模式可以确保在任何时间只有一个实例对象。
Classes implementing Singleton pattern will ensure that only one instance of the object ever exists at any one time.
使用类来实现单例模式可以确保在任何时间只有一个实例对象。
Classes implementing Singleton pattern will ensure that only one instance of the object ever exists at any one time.
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