公共静态工厂方法 [英] public static factory method
问题描述
首先，如果这是一个愚蠢的问题，请原谅我，我只是在尝试学习这种语言的核心.我正在阅读《有效的Java》，第一章讨论了静态工厂方法与构造方法.他们的利弊.令我困惑的几件事是:
First of all please forgive me if its a really dumb question, I am just trying to learn this language to its core. I am reading Effective Java and the very first chapter talks about Static factory methods vs. Constructors. Their pros and cons. Few things that are confusing to me are:
-
静态工厂方法返回的对象的
- 类是非公开的-究竟是什么意思?
- 与构造函数不同，每次调用新工厂都不需要使用静态工厂方法-这种情况如何发生?我仅使用工厂方法来获取新对象，我们是否将检查方法放入工厂方法中以检查对象是否已存在?
- class of an object returned by static factory method is nonpublic - what exactly does it mean?
- unlike constructors static factory methods are not required to create a new object each time they are invoked - How does this happen? I am invoking factory method only to obtain a new object and do we put a check in factory method for checking if object already exists?
谢谢.
推荐答案
静态工厂方法返回的对象的类是非公共的- 到底是什么意思?
class of an object returned by static factory method is nonpublic - what exactly does it mean?
这意味着静态工厂方法返回的对象的实际类可以是声明类型的子类，并且此子类不必是公共的.这只是客户端代码不关心的另一个实现细节.
It means that the actual class of the objects returned by a static factory method can be a subclass of the declared type, and this subclass does not have to be public. It's just another implementation detail that client code should not care about.
与构造函数不同，每次调用新工厂时，都不需要静态工厂方法来创建新对象-这是怎么发生的?我仅调用工厂方法来获取新对象，是否将检查方法放入工厂方法中以检查对象是否已存在?
unlike constructors static factory methods are not required to create a new object each > time they are invoked - How does this happen? I am invoking factory method only to obtain a new object and do we put a check in factory method for checking if object already exists?
是的，这是可以完成此操作的一种方式.但实际上，一切皆有可能.
Yes, that's one way this could be done. But really, anything is possible.
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