如何将java.util.List复制到另一个java.util.List中 [英] How to copy a java.util.List into another java.util.List

问题描述

我有一个从Web服务填充的列表< SomeBean> 。我想将该列表的内容复制/克隆到相同类型的空列表中。 Google搜索复制列表建议我使用 Collections.copy（）方法。在我看到的所有示例中，目标列表应包含要进行复制的项目的确切数量。

I have a List<SomeBean> that is populated from a Web Service. I want to copy/clone the contents of that list into an empty list of the same type. A Google search for copying a list suggested me to use Collections.copy() method. In all the examples I saw, the destination list was supposed to contain the exact number of items for the copying to take place.

由于我使用的列表是通过Web服务填充的，它包含数百个对象，我不能使用上面的技术。或者我使用它错了！无论如何，为了使它工作，我试图做这样的事情，但我仍然有一个 IndexOutOfBoundsException 。

As the list I am using is populated through a web service and it contains hundreds of objects, I cannot use the above technique. Or I am using it wrong??!! Anyways, to make it work, I tried to do something like this, but I still got an IndexOutOfBoundsException.

List<SomeBean> wsList = app.allInOne(template);

List<SomeBean> wsListCopy=new ArrayList<SomeBean>(wsList.size());   
Collections.copy(wsListCopy,wsList);
System.out.println(wsListCopy.size());

我尝试使用 wsListCopy = wsList.subList（0，wsList。 size（））但我在代码中有一个 ConcurrentAccessException 。命中和审判。 ：）

I tried to use the wsListCopy=wsList.subList(0, wsList.size()) but I got a ConcurrentAccessException later in the code. Hit and trial. :)

无论如何，我的问题很简单，如何将我的列表的整个内容复制到另一个列表中？课程。

Anyways, my question is simple, how can I copy the entire content of my list into another List? Not through iteration, of course.

推荐答案

只需使用：

List<SomeBean> newList = new ArrayList<SomeBean>(otherList);

注意：如果修改 otherList 从另一个线程，那么你可能想让 otherList （甚至 newList ）a CopyOnWriteArrayList ，例如 - 或使用锁原语，例如 ReentrantReadWriteLock 序列化对同时访问的任何列表的读/写访问。

Note: still not thread safe, if you modify otherList from another thread, then you may want to make that otherList (and even newList) a CopyOnWriteArrayList, for instance -- or use a lock primitive, such as ReentrantReadWriteLock to serialize read/write access to whatever lists are concurrently accessed.

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