陷入“java.util.ConcurrentModificationException”
这是我的代码：
// eventList is a LinkedList
public void run() {
Iterator<Event> it = eventList.iterator();
int size = eventList.size();
while(size > 0) {
while(it.hasNext()) {
Event e = it.next(); //flaged line
if(e.ready()) {
System.out.println(e);
e.action();
eventList.remove(e);
--size;
}
}
}
}
错误java.util.ConcurrentModificationException在标记内衬(Event e = it.next();)处抛出。您是否发现我的代码中存在一个错误，该错误清楚地表明了引发该异常的原因？
Here is my code:
// eventList is a LinkedList
public void run() {
Iterator<Event> it = eventList.iterator();
int size = eventList.size();
while(size > 0) {
while(it.hasNext()) {
Event e = it.next(); //flaged line
if(e.ready()) {
System.out.println(e);
e.action();
eventList.remove(e);
--size;
}
}
}
}
The error java.util.ConcurrentModificationException is thrown at the flag lined (Event e = it.next();). Do you see a mistake in my code that makes obvious the reason of that exception to be thrown?
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评论（2）
您正在修改
eventList，同时使用eventList.remove()进行迭代。您不能这样做，否则Iterator将变得不可用。只需将
eventList.remove(e)替换为it.remove()就可以了。此外，如果其中一个事件在第一次运行时未准备好，您很容易陷入无限循环，因为
it.hasNext()一旦返回就永远不会返回truefalse，但size也不会被修改。一种解决方案是将整个Iterator it = ...行移动到第一个while循环的内部。我还会修改外部
while循环以使用while (!e.isEmpty())而不是尝试跟踪eventList的大小手动。Your are modifying
eventListwhile usingeventList.remove()while iterating over it. You must not do this, or theIteratorbecomes unusable.Simply replace
eventList.remove(e)withit.remove()and it should be fine.Also, you can easily run into an endless loop if one of your events isn't ready in the first run because
it.hasNext()will never returntrueonce it returnedfalse, butsizewon't be modified either. One solution would be to move the wholeIterator it = ...line inside the firstwhileloop.I'd also modify the outer
whileloop to usewhile (!e.isEmpty())instead of trying to track the size ofeventListmanually.您应该通过迭代器删除元素，否则迭代器会因为底层集合发生更改而重置。
You should remove the element through the iterator, otherwise the iterator gets reset because the underlying collection changed.