LinkedList run out of the concurrentmodificationexception anomaly

Project, the Concurrentmodificationexception exception is thrown in the background when using LinkedList

See the source code found the problem, the analysis is as follows:

1. The outermost method of the exception (the method that throws the exception directly):

  final void Checkforcomodification ()    {      if (LinkedList.this.modCount! = this.expectedmodcount) {        throw New Concurrentmodificationexception ();}}}  

The field of the Modcount:linkedlist object, add (), and the Remove () action will perform the + + on the field.

Expectedmodcount: The iterator iterator the field of the object, and also the Add (), the remove operation will increment the field value.

2. Impersonation of the business method that throws the exception call:

<pre name= "code" class= "Java" >public class Test {public    static void Main (string[] args)  {        arraylist& lt;integer> list = new arraylist<integer> ();        List.add (2);        iterator<integer> Iterator = List.iterator ();        while (Iterator.hasnext ()) {            integer integer = Iterator.next ();            if (integer==2)                list.remove (integer);}}    }

InThe List object executes

List.add (2);

after its modcount ==1, and then generates iteratorobject, iterator of the Expectedmodcount==1, at which point the two values are consistent.

When executing <span style= "Font-family:verdana, Arial, Helvetica, Sans-serif;" >list.remove (integer); </span><span style= "Font-family:verdana, Arial, Helvetica, Sans-serif;" After >, note this time, </span><span style= "Font-family:verdana, Arial, Helvetica, Sans-serif;" >modcount ==2, while Expectedmodcount==1</span><span style= "Font-family:verdana, Arial, Helvetica, Sans-serif ; font-size:18px; line-height:28px; " ></span>

Down, as normal thinking, to execute again

while (Iterator.hasnext ()), the intuition is that I added an object to come in, this time, there should be no next element, so here will not come in.

The problem is here, because we just called list.remove (integer);
After execution, there is no effect on the internal iterator, so execute again

while (Iterator.hasnext ())

, the iterator internal judgment has not reached size, so it will continue to execute and then execute

Iterator.next ();

At this point, the next () method is executed first

Checkforcomodification ();

FoundModcount andExpectedmodcount inconsistent, throws an exception.

Speaking of which, everyone already understands.

Here's how to fix it:

public static void Main (string[] args)  {        linkedlist<integer> list = new linkedlist<integer> ();        List.add (2);        iterator<integer> Iterator = List.iterator ();        while (Iterator.hasnext ()) {            integer integer = Iterator.next ();            if (integer==2) {            iterator.remove ();}}    }

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LinkedList run out of the concurrentmodificationexception anomaly