我有以下代码，它给出了 java.util.concurrentmodificationexception。
我不是线程专家，但我认为如果我有一个同步列表，它应该是线程安全的......
编辑: 这是我的方法的完整代码。
@Override
protected List< ExportSchedule > export( List< ExportSchedule > exportSchedules )
{
final HandleSystemDoiAdministrator handleSystemDoiAdministrator = HandleSystemDoiAdministratorFactory.getInstance();
final List< ExportSchedule > successfullyExported = new ArrayList<>();
final List<ExportError> unsuccessfullyExported = Collections.synchronizedList( new ArrayList<ExportError>() );
ExecutorService executorService = Executors.newFixedThreadPool( 10 );
for ( final ExportSchedule exportSchedule : exportSchedules )
{
executorService.execute( new Runnable() {
public void run()
{
String doi = exportSchedule.getDoi().getDoi();
String url = exportSchedule.getDoi().getUrl();
boolean success = handleSystemDoiAdministrator.updateDoiHandle( doi, url );
if ( success )
{
successfullyExported.add( exportSchedule );
}
else
{
if ( handleSystemDoiAdministrator.isWarn() )
{
DoiErrorHelper.persistExportError(
ExportInterface.HANDLE_SERVER,
doi,
"Warning: Error exporting DOI " + doi + " with URL " + url + " to Handle Server: "
+ handleSystemDoiAdministrator.getResponseOutcome().toString(),
exportSchedule.getDoi().getDoiPool() );
}
if ( handleSystemDoiAdministrator.isFatal() )
{
synchronized(unsuccessfullyExported) {
unsuccessfullyExported.add( DoiErrorHelper.createExportError( doi, "Fatal: Error exporting DOI " + doi + " with URL " + url + " to Handle Server: "
+ handleSystemDoiAdministrator.getResponseOutcome().toString(), null, new Date(), exportSchedule.getDoi().getDoiPool().getName(),
exportSchedule.getDoi().getDoiPool().getDoiPrefix(), ExportInterface.HANDLE_SERVER ) );}
}
}
}
} );
}
executorService.shutdown();
try
{
executorService.awaitTermination( 1, TimeUnit.MINUTES );
}
catch ( InterruptedException e )
{
// TODO Auto-generated catch block
e.printStackTrace();
}
return successfullyExported;
}
编辑 2:
这是错误:
[exec]
[exec] [#|2014-05-08T10:16:12.951+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=203;_ThreadName=Thread-2;| at java.util.HashMap$HashIterator.nextEntry(HashMap.java:894)|
#]
[exec]
[exec] [#|2014-05-08T10:16:12.951+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=203;_ThreadName=Thread-2;| at java.util.HashMap$EntryIterator.next(HashMap.java:934)|#]
[exec]
[exec] [#|2014-05-08T10:16:12.951+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=203;_ThreadName=Thread-2;| at java.util.HashMap$EntryIterator.next(HashMap.java:932)|#]
[exec]
[exec] [#|2014-05-08T10:16:12.952+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=203;_ThreadName=Thread-2;| at java.util.AbstractMap.toString(AbstractMap.java:518)|#]
[exec]
[exec] [#|2014-05-08T10:16:12.952+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=203;_ThreadName=Thread-2;| at ch.ethz.id.wai.doi.export.handle.DoiExport2HSProcessing$1.r
un(DoiExport2HSProcessing.java:106)|#]
[exec]
[exec] [#|2014-05-08T10:16:12.952+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=203;_ThreadName=Thread-2;| at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoo
lExecutor.java:1145)|#]
[exec]
[exec] [#|2014-05-08T10:16:12.952+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=203;_ThreadName=Thread-2;| at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPo
olExecutor.java:615)|#]
[exec]
[exec] [#|2014-05-08T10:16:12.953+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=203;_ThreadName=Thread-2;| at java.lang.Thread.run(Thread.java:722)|#]
[exec]
[exec] [#|2014-05-08T10:16:28.552+0200|INFO|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=157;_ThreadName=Thread-2;|0|#]
[exec]
[exec] [#|2014-05-08T10:16:31.221+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=222;_ThreadName=Thread-2;|Exception in thread "pool-41-thread-10" |#]
[exec]
[exec] [#|2014-05-08T10:16:31.223+0200|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=222;_ThreadName=Thread-2;|java.util.ConcurrentModificationException
[exec] at java.util.HashMap$HashIterator.nextEntry(HashMap.java:894)
[exec] at java.util.HashMap$EntryIterator.next(HashMap.java:934)
[exec] at java.util.HashMap$EntryIterator.next(HashMap.java:932)
[exec] at java.util.AbstractMap.toString(AbstractMap.java:518)
[exec] at ch.ethz.id.wai.doi.export.handle.DoiExport2HSProcessing$1.run(DoiExport2HSProcessing.java:106)
[exec] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
[exec] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
[exec] at java.lang.Thread.run(Thread.java:722)
[exec] |#]
DoiExport2HSProcessing.java 是包含该方法的类，第 106 行是我将错误添加到列表的地方。
最佳答案
ConcurrentModificationException 与同步或线程安全没有直接关系。多个线程将使此异常的条件(见下文)不可见，但它也可以在一个线程中发生!
同步列表可防止您从处于未定义状态的多个线程访问列表。但是您仍然可以在修改列表时迭代元素。这将导致 ConcurrentModificationException。
在迭代过程中，您不得修改列表，使用add()、remove() 等。唯一有效的修改是使用 Iterator(remove())或 ListIterator(add() 和set())!
关于java - 是什么导致使用 Collections.synchronizedList 的 java.util.concurrentmodificationexception？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23536074/