调用在Java中的foreach循环中删除 [英] Calling remove in foreach loop in Java

问题描述

在Java中，使用foreach循环迭代集合时调用集合上的remove是否合法？例如：

  List< String> names = .... 
（String name：names）{
 //做某事
 names.remove（name）。 
 
 
 
 
 
 $ p 
作为附录，删除尚未迭代的项目是否合法然而？例如，
 
 
  //假设名称列表为重复条目
 List< String> （String name：names）{
 //做某事
 while（names.remove（name））; 
 
  
 
 
解决方案
例如：
 
 
 <$ c $在迭代它的时候，你应该使用一个Iterator。
 
 
 C>列表与LT;字符串> names = .... 
 Iterator< String>我= names.iterator（）; 
 while（i.hasNext（））{
 String s = i.next（）; //必须先调用i.remove（）
 //做某事
 i.remove（）; 
 
  
从
 
 
  p>这个类的迭代器和listIterator 
方法返回的迭代器是快速失败的：如果在创建迭代器后的任何
时间结构上修改列表，除了通过
迭代器自己的删除或添加方法，迭代器将抛出
 ConcurrentModificationException。因此，面对并发的
修改，迭代器会快速而干净地失败，而不是在
将来在未定的时间
冒着任意的，非确定性的行为。
 
 
也许很多新手不清楚的是，使用for / foreach构造迭代列表隐式地创建了一个必须不可访问的迭代器。这些信息可以在这里找到
 
In Java, is it legal to call remove on a collection when iterating through the collection using a foreach loop?  For instance:
List<String> names = ....
for (String name : names) {
   // Do something
   names.remove(name).
}
As an addendum, is it legal to remove items that have not been iterated over yet? For instance, 
//Assume that the names list as duplicate entries
List<String> names = ....
for (String name : names) {
    // Do something
    while (names.remove(name));
}

解决方案
To safely remove from a collection while iterating over it you should use an Iterator.

For example:
List<String> names = ....
Iterator<String> i = names.iterator();
while (i.hasNext()) {
   String s = i.next(); // must be called before you can call i.remove()
   // Do something
   i.remove();
}
From the Java Documentation :

  
The iterators returned by this class's iterator and listIterator
  methods are fail-fast: if the list is structurally modified at any
  time after the iterator is created, in any way except through the
  iterator's own remove or add methods, the iterator will throw a
  ConcurrentModificationException. Thus, in the face of concurrent
  modification, the iterator fails quickly and cleanly, rather than
  risking arbitrary, non-deterministic behavior at an undetermined time
  in the future.
Perhaps what is unclear to many novices is the fact that iterating over a list using the for/foreach constructs implicitly creates an iterator which is necessarily inaccessible. This info can be found here

                        
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