Java 中的克隆列表

发布于 2024-12-27 11:53:31 字数 1038 浏览 2 评论 0原文

可能的重复：
如何克隆 ArrayList 并克隆其内容？

我有一个 ArrayList，我想“深度”克隆，以便对原始列表中的任何项目进行修改不会对克隆列表中的项目产生任何影响：

ArrayList<Widget> origList = getMyList();
ArrayList<Widget> cloneList = origList.clone();

// Remove the 5th Widget from the origina list
origList.remove(4);

// However, the cloneList still has the 5th Widget and is unchanged

// Change the id of the first widget
origList.get(0).setId(20);

// However in cloneList, the 1st Widget's ID is not 20

什么是实现这一目标的最佳/最安全方法？我想这并不那么简单：

ArrayList<Widget> cloneList = origList.clone();

我想这是一个内置的 ArrayList 类型，再加上它的泛型这一事实，将使事情变得复杂。我还想象我需要为我的 Widget 类编写一个特殊的 clone() 重写？

提前致谢！

编辑：
如果有一个公共 JAR 可以为我完成这项繁重的工作，我也会完全接受，所以请随意提出建议，但是我仍然想知道如何以 ole' 时尚的方式做到这一点，这样我就可以学习 ;-）

原文

Possible Duplicate:
How to clone ArrayList and also clone its contents?

I have a ArrayList<Widget> that I would like to "deep" clone so that making modifications to any items in the original list does not have any effect on the items in the cloned list:

ArrayList<Widget> origList = getMyList();
ArrayList<Widget> cloneList = origList.clone();

// Remove the 5th Widget from the origina list
origList.remove(4);

// However, the cloneList still has the 5th Widget and is unchanged

// Change the id of the first widget
origList.get(0).setId(20);

// However in cloneList, the 1st Widget's ID is not 20

What's the best/safest way of accomplishing this? I imagine that it's not as simple as:

ArrayList<Widget> cloneList = origList.clone();

I imagine the fact that this is a built-in ArrayList type, plus the fact that its generic, are going to complicate things. I also imagine I will need to write a special clone() override for my Widget class?

Thanks in advance!

Edit:
I'd also be completely receptive if there is a commons JAR out there that does this heavy lifting for me, so please feel free to make suggestions, however I would still like to know how to do this the ole' fashion way so I can learn ;-)

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你不是我要的菜∠ 2025-01-03 11:53:31

这是一项艰巨的任务，我建议您使用可用的库之一，例如 http:// code.google.com/p/cloning/

另请参阅：Java：深度克隆/复制实例的推荐解决方案

如果您想了解它是如何完成的，获取开源库并查看源代码:)

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于我来说 2025-01-03 11:53:31

您需要迭代原始列表中的每个项目并单独克隆每个项目，然后将它们添加到“克隆”项目的新列表中。

类似的：

List<Widget> origList = getMyList();
List<Widget> clonedList = clone(origList);

private List<Widget> clone(List<Widget> listToClone) {
  List<Widget> clonedList = new LinkedList<Widget>();

  for (Widget widget : listToClone) {
    clonedList.add(widget.clone());
  }

  return clonedList;
}

要实现此功能，您必须让 Widget 对象实现 Cloneable 接口和 clone() 方法。不需要其他任何东西。

但正如其他发帖者所说，许多人会认为 Java 中的克隆实现不太值得依赖，最好避免。

You need to iterate over each item in the original list and clone each item individually, then add them to a new list of 'cloned' items.

Something like:

List<Widget> origList = getMyList();
List<Widget> clonedList = clone(origList);

private List<Widget> clone(List<Widget> listToClone) {
  List<Widget> clonedList = new LinkedList<Widget>();

  for (Widget widget : listToClone) {
    clonedList.add(widget.clone());
  }

  return clonedList;
}

For this to work you will have to have your Widget object implement the Cloneable interface, and the clone() method. Nothing else is needed.

But again, as the other posters have said, many would argue that the clone implementation in Java isn't great to rely on, and is best avoided.

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