Java ConcurrentModificationException [英] Java ConcurrentModificationException
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问题描述
当删除第二个元素时,没有ConcurrentModificationException
when remove the second last element there is no ConcurrentModificationException
List<String> myList1 = new ArrayList<String>();
Collections.addAll(myList1, "str1","str2","str3","str4","str5");
for(String element : myList1){//no ConcurrentModificationException here
if(element.equalsIgnoreCase("str4"))
myList1.remove("str4");
}
System.out.println(myList1);
但是当删除其他元素时,会出现一个ConcurrentModificationException
But when remove other elements there is a ConcurrentModificationException
List<String> myList2 = new ArrayList<String>();
Collections.addAll(myList2, "str1","str2","str3","str4","str5");
for(String element : myList2){//ConcurrentModificationException here
if(element.equalsIgnoreCase("str1"))
myList2.remove("str1");
}
System.out.println(myList2);
原因是什么?
推荐答案
我看到同样的事情,
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class Launcher
{
public static void main(String[] args)
{
doThis();
doThat();
}
private static void doThis()
{
System.out.println("dothis");
try
{
List<String> myList1 = new ArrayList<String>();
Collections.addAll(myList1, "str1","str2","str3","str4","str5");
for(String element : myList1){//no ConcurrentModificationException here
if(element.equalsIgnoreCase("str4"))
myList1.remove("str4");
}
System.out.println(myList1);
}
catch(Exception e)
{
e.printStackTrace();
}
}
private static void doThat()
{
System.out.println("dothat");
try
{
List<String> myList2 = new ArrayList<String>();
Collections.addAll(myList2, "str1","str2","str3","str4","str5");
for(String element : myList2){//ConcurrentModificationException here
if(element.equalsIgnoreCase("str1"))
myList2.remove("str1");
}
System.out.println(myList2);
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
哪些输出,
dothis
[str1, str2, str3, str5]
dothat
java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
at java.util.AbstractList$Itr.next(Unknown Source)
at com.foo.Launcher.doThat(Launcher.java:41)
at com.foo.Launcher.main(Launcher.java:12)
< hr>
我发现 原因 。
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