克隆 GregorianCalendar 的最快方法是什么?
我正在尝试制作一个对象的深层副本，包括一个 GregorianCalendar 实例.我总是对使用 clone() 持谨慎态度，而且这里似乎没有被覆盖，所以我只是逐个字段地进行复制.理想情况下，会有一个复制构造函数，我可以像这样使用它:
I'm trying to make a deep copy of an object, including a GregorianCalendar instance. I'm always wary of using clone() and it doesn't seem to have been overridden here, so I'm just doing the copy field by field. Ideally, there'd be a copy constructor, which I could use like so:
GregorianCalendar newCalendar = new GregorianCalendar(oldCalendar);
不幸的是，我在 API 中找不到任何此类功能，并且一直在试图找出我需要哪些字段才能获得准确的副本.那么，要复制其中一个日历，你会怎么做呢?我在这里错过了一些简单的快捷方式吗?
Unfortunately I can't find any such functionality in the API and am stuck trying to figure out which fields I need to get an exact copy. So, to make a copy of one of these calendars, how would you do it? Am I missing some simple shortcut here?
推荐答案
java.util.Calendar 已经覆盖了正在工作的 clone()，所以使用它.此外，Calendar 没有很深的数据层次——它的数据主要是 ints.
java.util.Calendar has overridden clone() which is working, so use it. Furthermore, Calendar doesn't have a deep data hierarchy — its data are mainly ints.
要扩展答案，您可以调用 SerializationUtils.clone(...) (来自 Apache commons-lang)在任何进行深拷贝的对象上，如果整个数据层次结构实现 Serializable.
To extend the answer, you can call SerializationUtils.clone(…) (from Apache commons-lang) on any object which makes a deep copy, if the whole data hierarchy implements Serializable.
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