在HashMap中澄清@ConcurrentModificationException [英] Clarification @ConcurrentModificationException in HashMap

问题描述

我希望在下面的代码中出现一个ConcurrentModificationException，但是它工作正常.

I am expecting a ConcurrentModificationException in the follow code, but it's working fine.

HashMap<Integer, String>table1 = new HashMap<Integer, String>();
    table1.put(1, "Sam");
    table1.put(2, "Jon");
    table1.put(3, "Doe");

    Iterator itr1 = table1.entrySet().iterator();

    table1.put(3, "DONN");
    while(itr1.hasNext())
    {
        System.out.println("---Value--" + itr1.next());
    }

根据HashMap的JavaDoc:

As per the JavaDoc for HashMap:

此类的所有集合视图方法"返回的迭代器都是快速失败的:如果在创建迭代器后的任何时间对结构进行结构修改，则除了通过迭代器自己的remove方法之外，该迭代器将以任何方式进行迭代抛出ConcurrentModificationException.

The iterators returned by all of this class's "collection view methods" are fail-fast: if the map is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove method, the iterator will throw a ConcurrentModificationException.

因此，由于我在获取Iterator之后修改了HashMap，因此我应该获取了ConcurrentModificationException.为什么不扔?

So since I am modifying the HashMap after getting the Iterator I should be getting the ConcurrentModificationException. Why is it not throwing?

推荐答案

为现有键输入条目在当前HashMap，并且永远不会触发ConcurrentModificationException.尝试使用新钥匙，例如table1.put(4, "UPS");以获得ConcurrentModificationException.

Putting an entry for an existing key is not considered a structural modification in the current implementation of HashMapand will never trigger a ConcurrentModificationException. Try putting with a new key, e.g. table1.put(4, "UPS"); to get a ConcurrentModificationException.

这篇关于在HashMap中澄清@ConcurrentModificationException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！