如何将一个ArrayList的内容复制到另一个？ [英] How do I copy the contents of one ArrayList into another?

问题描述

我有一些数据结构，我想使用一个作为临时数据，另一个不是临时数据。

I have some data structures, and I would like to use one as a temporary, and another as not temporary.

ArrayList<Object> myObject = new ArrayList<Object>();
ArrayList<Object> myTempObject = new ArrayList<Object>();


//fill myTempObject here
....

//make myObject contain the same values as myTempObject
myObject = myTempObject;

//free up memory by clearing myTempObject
myTempObject.clear();

现在问题当然是 myObject 实际上只是指向 myTempObject ，因此一旦 myTempObject 被清除，那么 myObject 。

now the problem with this of course is that myObject is really just pointing to myTempObject, and so once myTempObject is cleared, so is myObject.

如何在<$ c $中保留 myTempObject 中的值c> myObject 使用java？

How do I retain the values from myTempObject in myObject using java?

推荐答案

你可以使用这样的技巧：

You can use such trick:

myObject = new ArrayList<Object>(myTempObject);

或使用

myObject = (ArrayList<Object>)myTempObject.clone();

您可以获得有关clone（）方法的一些信息这里

You can get some information about clone() method here

但是你应该记住，所有这些方法都会为你提供列表的副本，而不是它的所有元素。因此，如果您更改复制列表中的某个元素，它也会在原始列表中更改。

But you should remember, that all these ways will give you a copy of your List, not all of its elements. So if you change one of the elements in your copied List, it will also be changed in your original List.

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