問題描述
我正在嘗試制作一個對象的深層副本，包括一個 GregorianCalendar 實例.我總是對使用 clone() 持謹慎態度，而且這里似乎沒有被覆蓋，所以我只是逐個字段地進行復制.理想情況下，會有一個復制構造函數，我可以像這樣使用它:
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 中找不到任何此類功能，并且一直在試圖找出我需要哪些字段才能獲得準確的副本.那么，要復制其中一個日歷，你會怎么做呢?我在這里錯過了一些簡單的快捷方式嗎?
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?
推薦答案
java.util.Calendar 已經覆蓋了正在工作的 clone()，所以使用它.此外，Calendar 沒有很深的數據層次——它的數據主要是 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.
要擴展答案，您可以調用 SerializationUtils.clone(...) (來自 Apache commons-lang)在任何進行深拷貝的對象上，如果整個數據層次結構實現 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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