For 循环中的 java.util.ConcurrentModificationException
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/19702461/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
java.util.ConcurrentModificationException in For loop
提问by EsmaeelQash
I am trying to program an IM software, I want to let user leave the conversation and tell his partner that he has left... I prefer to use for loop instead Iterator, seek all the users and get the user who ask to leave and remove him... like that:
我正在尝试编写一个 IM 软件，我想让用户离开对话并告诉他的伙伴他已经离开了......我更喜欢使用 for 循环而不是迭代器，寻找所有用户并让要求离开的用户和删除他......就像这样：
for(Clientuser Cu: EIQserver.OnlineusersList)
if(Cu.ID.equals(thsisUser.ID)) // find the user who ask to leave
{
Omsg.setBody("@@!&$$$$@@@####$$$$"); //code means : clien! ur parter leaves...
sendMessage(Omsg); // sed message to thje partner with that code
EIQserver.OnlineusersList.remove(Cu);// remove the partner
EIQserver.COUNTER--;// decrease counter.
}
I get Exception: java.util.ConcurrentModificationException
我得到异常：java.util.ConcurrentModificationException
I was using iterators, and to get rid of this exception, I convert to for, but the same exception still appears!! how may I get rid of this exception?
我正在使用迭代器，为了摆脱这个异常，我转换为 for，但仍然出现相同的异常！！我怎样才能摆脱这个例外？
采纳答案by Konstantin Yovkov
Use Iteratorinstead of looping. For example:
使用迭代器而不是循环。例如：
Iterator<Clientuser> iterator = EIQserver.OnlineusersList.iterator();
while (iterator.hasNext()) {
Clientuser next = iterator.next();
if(next.ID.equals(thsisUser.ID)) {
Omsg.setBody("@@!&$$$$@@@####$$$$");
sendMessage(Omsg);
iterator.remove();// remove the partner
}
}
回答by afk5min
Faulting line:
EIQserver.OnlineusersList.remove(Cu);
故障线路：
EIQserver.OnlineusersList.remove(Cu);
You can only remove elements from a collection that is being iterated over via the Iteratorobject you are using to iterate.
您只能从正在通过Iterator您用于迭代的对象迭代的集合中删除元素。
for (Iterator<Clientuser> it = EIQserver.OnlineusersList.iterator(); it.hasNext();)
{
Clientuser cu = it.next();
if (!cu.ID.equals(thsisUser.ID))
continue;
// other code
it.remove();
}
回答by Debabrata
As you are Iterating the EIQserver collection class, you can not remove element from the same class. Use a different collection for Iteration and remove the element from EIQserver class.
当您迭代 EIQserver 集合类时，您不能从同一个类中删除元素。使用不同的迭代集合并从 EIQserver 类中删除元素。
List temp = ListofEIQserverobject;
for(Clientuser Cu: temp.OnlineusersList){
..... your code then
EIQserver.OnlineusersList.remove(Cu);
}
回答by Trick
One possible solution is also to transform the Collection to HashMap, save id's to remove and then remove it from the HashMap.
一种可能的解决方案也是将集合转换为 HashMap，保存要删除的 id，然后将其从 HashMap 中删除。
Collection<Integer> removeIds = new ArrayList<Integer>();
Map<Integer,ClientUser> all = new HashMap<Integer,ClientUser>();
for(Clientuser Cu: EIQserver.OnlineusersList) {
all.put(cu.ID,Cu);
if(Cu.ID.equals(thsisUser.ID)) // find the user who ask to leave
{
Omsg.setBody("@@!&$$$$@@@####$$$$"); //code means : clien! ur parter leaves...
sendMessage(Omsg); // sed message to thje partner with that code
EIQserver.COUNTER--;// decrease counter.
removeIds.add(Cu.ID);
}
}
回答by SeniorJD
Use Iteratorfor do something with list in loop:
使用Iterator用于做一些与环路列表：
Iterator<Clientuser> iter = EIQserver.OnlineuserList.iterator();
for(;iter.hasNext();) {
Clientuser Cu = iterator.next();
if(Cu.ID.equals(thsisUser.ID)) {
Omsg.setBody("@@!&$$$$@@@####$$$$");
sendMessage(Omsg);
iterator.remove(next);
}
}
