ADDITIONAL SYSTEM INFORMATION :
Windows 8.1
Java 11.0.2+9

A DESCRIPTION OF THE PROBLEM :
When java.util.ServiceLoader concurrently acts as an iterator exceptions are thrown due to a race condition in the ServiceLoader implementation.

Effects of this behavior have also been reported elsewhere, e.g.:
https://github.com/eclipse/paho.mqtt.java/issues/572
https://github.com/talsma-ict/context-propagation/issues/8


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the following test program below until exceptions occur.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
No exceptions.
ACTUAL -

Exception in thread "Thread-39" java.util.NoSuchElementException
at java.base/java.lang.CompoundEnumeration.nextElement(ClassLoader.java:3036)
at java.base/java.util.ServiceLoader$LazyClassPathLookupIterator.nextProviderClass(ServiceLoader.java:1205)
at java.base/java.util.ServiceLoader$LazyClassPathLookupIterator.hasNextService(ServiceLoader.java:1220)
at java.base/java.util.ServiceLoader$LazyClassPathLookupIterator.hasNext(ServiceLoader.java:1264)
at java.base/java.util.ServiceLoader$2.hasNext(ServiceLoader.java:1299)
at java.base/java.util.ServiceLoader$3.hasNext(ServiceLoader.java:1384)
at de.uplanet.lucy.server.mqtt.JdkBug.bugsGoHere(JdkBug.java:39)
at de.uplanet.lucy.server.mqtt.JdkBug.lambda$0(JdkBug.java:28)
at java.base/java.lang.Thread.run(Thread.java:834)
Exception in thread "Thread-37" java.util.NoSuchElementException
at java.base/jdk.internal.loader.URLClassPath$1.nextElement(URLClassPath.java:356)
at java.base/jdk.internal.loader.URLClassPath$1.nextElement(URLClassPath.java:331)
at java.base/jdk.internal.loader.BuiltinClassLoader$1.hasNext(BuiltinClassLoader.java:358)
at java.base/jdk.internal.loader.BuiltinClassLoader$1.hasMoreElements(BuiltinClassLoader.java:365)
at java.base/java.lang.CompoundEnumeration.next(ClassLoader.java:3022)
at java.base/java.lang.CompoundEnumeration.hasMoreElements(ClassLoader.java:3031)
at java.base/java.util.ServiceLoader$LazyClassPathLookupIterator.nextProviderClass(ServiceLoader.java:1202)
at java.base/java.util.ServiceLoader$LazyClassPathLookupIterator.hasNextService(ServiceLoader.java:1220)
at java.base/java.util.ServiceLoader$LazyClassPathLookupIterator.hasNext(ServiceLoader.java:1264)
at java.base/java.util.ServiceLoader$2.hasNext(ServiceLoader.java:1299)
at java.base/java.util.ServiceLoader$3.hasNext(ServiceLoader.java:1384)
at de.uplanet.lucy.server.mqtt.JdkBug.bugsGoHere(JdkBug.java:39)
at de.uplanet.lucy.server.mqtt.JdkBug.lambda$0(JdkBug.java:28)
at java.base/java.lang.Thread.run(Thread.java:834)


---------- BEGIN SOURCE ----------
import java.security.Provider;
import java.util.ServiceLoader;

public final class JdkBug
{
  private static final ServiceLoader<Provider> SERVICE_LOADER =
    ServiceLoader.load(Provider.class, Provider.class.getClassLoader());


  public static void main(String[] args) throws Exception
  {
    for (int i = 0; i < 50; i++)
      new Thread(() -> bugsGoHere()).start();

    Thread.sleep(10000L);
  }


  public static void bugsGoHere()
  {
    int i = 0;

    for (java.security.Provider prov : SERVICE_LOADER) // throws the NoSuchElementException
    {
      if (prov.isConfigured())
        i++;
    }
  }
}

---------- END SOURCE ----------