当删除倒数第二个元素时,没有 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 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);
是什么原因?
我也看到同样的事情
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();
}
}
}
其输出,
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)
我发现原因 https://stackoverflow.com/questions/14673653/why-isnt-this-code-causing-a-concurrentmodificationexception.
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