java - 并发HashMap迭代

Question

ConcurrentHashMap是线程安全的，因此我们可以在迭代时更新Map的值。但以下程序的输出并不符合我的预期。

Map concurrentHashMap = new ConcurrentHashMap<();
concurrentHashMap.put("0", "b");
Iterator iterator = concurrentHashMap.entrySet().iterator();
concurrentHashMap.put("8", "k");
concurrentHashMap.put("2", "c");
concurrentHashMap.put("3", "d");
concurrentHashMap.put("1", "e");        
    
while(iterator.hasNext())
{
    System.out.println(""+iterator.next());
}

上述代码的输出是

0=b

8=k

3=d

2=c

预期输出

1=e

0=b

8=k

3=d

2=c

Answer 1

来自 ConcurrentHashMap.entrySet() 的文档:

The view's iterator is a "weakly consistent" iterator that will never throw ConcurrentModificationException, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.