您对HashMap的迭代器是快速失败而HashTable的枚举器不是t到底是什么意思? [英] What do you exactly mean by HashMap's iterator is fail-fast and HashTable's enumerator isn't?

问题描述

我一直在寻找两个类之间的区别，而这个博客的出处是很多答案. http://javarevisited.blogspot.com/2010/10/difference-between-hashmap-and.html

I was looking up the difference between the two classes and this point came up in a lot of the answers with this blog being the source: http://javarevisited.blogspot.com/2010/10/difference-between-hashmap-and.html

但是我没有完全理解它.有人可以详细说明吗?也许举个例子?

However I don't completely get it. Can someone elaborate this? Perhaps with an example?

感谢您的光临！

推荐答案

快速失败"是指在遍历内容时尝试修改内容时，它将失败并引发ConcurrentModificationException.

Fail-fast means when you try to modify the content when you are iterating thru it, it will fail and throw ConcurrentModificationException.

Set keys = hashMap.keySet();
for (Object key : keys) {
    hashMap.put(someObject, someValue); //it will throw the ConcurrentModificationException here
} 

对于HashTable枚举:

For HashTable enumeration:

 Enumeration keys = hashTable.keys();
 while (keys.hasMoreElements()) {
          hashTable.put(someKey, someValue);  //this is ok
    }

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