Java：如何从列表中删除元素，同时迭代/添加它 [英] Java: How to remove elements from a list while iterating over/adding to it

问题描述

此问题是在这个问题。

我有两种方法，stopAndRemove（ServerObject服务器）和close（）方法。后者应关闭所有服务器并将其从服务器列表中删除。该列表被定义为

  List< ServerObject>服务器。 
  

我不想在closeCurrentlyOpen中使用stopAndRemove几乎相同的代码，所以我想做一些事情例如：

  public void closeCurrentlyOpen（）{
 for（ServerObject server：this.servers）{
 stopAndRemove（server）
} 
} 
  

这将导致ConcurrentModificationException。我尝试复制列表

  List< ServerObject> copyList = new ArrayList< ServerObject>（this.servers）; 
  

并使用它作为foreach循环的列表。但是，然后它可能是另一个线程附加一个服务器到服务器列表，而我迭代copyList但closeCurrentlyOpen应该导致一个emtpy列表。
由于addServerToList方法被同步到servers-list，这样做

  public void closeCurrentlyOpen（）{
 synchronized（this.servers）{
 for（ServerObject server：this.servers）{
 stopAndRemove（server）
} 
} 
} 
  

将解决修改问题。但是我不能同步stopAndRemove方法中的代码，如果直接调用它是必要的。

我觉得这三个方法的设计可能需要一个研究。
任何人的想法？

解决方案

从stopAndRemove（）分离一个方法stop然后使用显式迭代器编写循环，执行stop和iterator.remove（）。

和在方法名称中是一个代码气味。 >

This question is a more special case of the problem described (and solved) in this question.

I have two methods, stopAndRemove(ServerObject server) and a close() method. The later should close all servers and remove them from the server list. The list is defined as

List<ServerObject> server. 

I do not want to have almost the same code from stopAndRemove in closeCurrentlyOpen, so I want to do something like:

public void closeCurrentlyOpen() {
   for(ServerObject server : this.servers) {
       stopAndRemove(server)
   }
}

This won't work, as this will cause a ConcurrentModificationException. I tried to make a copy of the list

List<ServerObject> copyList = new ArrayList<ServerObject>(this.servers);

and use that as the list for the foreach-loop. But then it might be possible that an other thread appends a Server to the servers list while I am iterating over copyList but closeCurrentlyOpen is supposed to result in an emtpy list. As the addServerToList method is synchronized to the servers-list, doing this

public void closeCurrentlyOpen() {
   synchronized(this.servers) {
     for(ServerObject server : this.servers) {
        stopAndRemove(server)
     }
    }
}

will solve the problem with modifications. But then I can not synchronize the code in the stopAndRemove method which is necessary if it is directly called.

I seems to me that the design of this three methods probably needs a workover. Ideas anybody?

解决方案

Split off a method stop() from stopAndRemove(). Then write the loop with an explicit iterator, do the stop and then iterator.remove().

"and" in a method name is a code smell.

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