如何将 java.util.List 复制到另一个 java.util.List [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 List.我想将该列表的内容复制/克隆到相同类型的空列表中.谷歌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，目标列表应该包含要进行复制的确切项目数.

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，并且它包含数百个对象，因此我无法使用上述技术.还是我用错了??！！无论如何，为了让它工作，我尝试做这样的事情，但我仍然得到一个 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()) 但我在代码后面得到了一个 ConcurrentAccessException.打击和审判.:)

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，如何将我的列表的全部内容复制到另一个列表中?当然不是通过迭代.

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

就用这个:

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

注意:仍然不是线程安全的，如果您从另一个线程修改 otherList，那么您可能希望使该 otherList(甚至 newList>) 一个 CopyOnWriteArrayList，例如 -- 或使用锁定原语，例如 ReentrantReadWriteLock 序列化对并发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.

这篇关于如何将 java.util.List 复制到另一个 java.util.List的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！