FULL PRODUCT VERSION :
java version "1.9.0-ea"
Java(TM) SE Runtime Environment (build 1.9.0-ea-b78)
Java HotSpot(TM) Client VM (build 1.9.0-ea-b78, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
I have a small webstart app which relies on the platform MBean server. The code to load this now fails under webstart with JDK 1.9, although not when run as a Java app from a jar file with java -jar

REGRESSION. Last worked in version 8u60

ADDITIONAL REGRESSION INFORMATION:
java version "1.9.0-ea"
Java(TM) SE Runtime Environment (build 1.9.0-ea-b78)
Java HotSpot(TM) Client VM (build 1.9.0-ea-b78, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Compile the given source code
2. Make and sign a jar file and deploy as webstart app
3. Run the corresponding JNLP file

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The application should terminate normally
ACTUAL -
The application does not launch correctly

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.NoClassDefFoundError: com/sun/management/internal/GarbageCollectorExtImpl
at sun.management.MemoryImpl.getMemoryManagers0(Native Method)
at sun.management.MemoryImpl.getMemoryManagers(MemoryImpl.java:98)
at sun.management.ManagementFactoryHelper.getGarbageCollectorMXBeans(ManagementFactoryHelper.java:130)
at java.lang.management.DefaultPlatformMBeanProvider$4.nameToMBeanMap(DefaultPlatformMBeanProvider.java:185)
at java.lang.management.ManagementFactory.lambda$getPlatformMBeanServer$0(ManagementFactory.java:478)
at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:269)
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:177)
at java.util.HashMap$ValueSpliterator.forEachRemaining(HashMap.java:1664)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:430)
at java.lang.management.ManagementFactory.getPlatformMBeanServer(ManagementFactory.java:479)
at Test.main(Test.java:3)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:504)
at com.sun.javaws.Launcher.executeApplication(Unknown Source)
at com.sun.javaws.Launcher.executeMainClass(Unknown Source)
at com.sun.javaws.Launcher.doLaunchApp(Unknown Source)
at com.sun.javaws.Launcher.run(Unknown Source)
at java.lang.Thread.run(Thread.java:746)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.lang.management.*;
import javax.management.*;

public class Test {
  public static void main(String... argv) throws Exception {
    final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer ();
    System.out.println(System.getProperty("user.home"));
  }
}
---------- END SOURCE ----------