Make sure you're doing the following

• You're using the latest build for your server version
• This isn't an issue caused by another plugin
• You've checked for duplicate issues
• You didn't use /reload

Describe the question
I was running 59 plugins on java 11 with protocol lib working great, then I switch to java 16 because my paper version and viaverision/viabackwards/viarewind all need the update to work. after I switched to java 16 and removed 1 unrelated plugin I got this console error saying to make a thread here.

API method(s) used
not sure what this means

Expected behavior
I didn't expect anything to happen but I got an error. maybe it was on my end but im not sure

Code
[19:07:51 INFO]: Error Cannot compile structure. Disabing compiler. (java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @112400db) occured in com.comphenix.protocol.reflect.compiler.BackgroundCompiler@797a532c.
[19:07:51 ERROR]: [ProtocolLib] INTERNAL ERROR: Cannot compile structure. Disabing compiler.
If this problem hasn't already been reported, please open a ticket
at https://github.com/dmulloy2/ProtocolLib/issues with the following data:
Stack Trace:
java.lang.reflect.InaccessibleObjectException: Unable to make protected final java.lang.Class java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int) throws java.lang.ClassFormatError accessible: module java.base does not "opens java.lang" to unnamed module @112400db
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:357)
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:297)
at java.base/java.lang.reflect.Method.checkCanSetAccessible(Method.java:199)
at java.base/java.lang.reflect.Method.setAccessible(Method.java:193)
at com.comphenix.protocol.reflect.compiler.StructureCompiler.generateClass(StructureCompiler.java:299)
at com.comphenix.protocol.reflect.compiler.StructureCompiler.compile(StructureCompiler.java:213)
at com.comphenix.protocol.reflect.compiler.BackgroundCompiler$2.call(BackgroundCompiler.java:204)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
at java.base/java.lang.Thread.run(Thread.java:831)
Dump:
Parameters:
com.comphenix.protocol.reflect.StructureModifier@4784bda7[
targetType=class net.minecraft.server.v1_16_R3.PacketPlayInBlockPlace
target=
converter=
fieldType=class java.lang.Object
data=[private net.minecraft.server.v1_16_R3.EnumHand net.minecraft.server.v1_16_R3.PacketPlayInBlockPlace.a, public long net.minecraft.server.v1_16_R3.PacketPlayInBlockPlace.timestamp]
defaultFields={private net.minecraft.server.v1_16_R3.EnumHand net.minecraft.server.v1_16_R3.PacketPlayInBlockPlace.a=0}
subtypeCache={}
customConvertHandling=false
useStructureCompiler=true
]
manager:
com.comphenix.protocol.injector.PacketFilterManager@3483eead[
unhookTask=com.comphenix.protocol.injector.DelayedSingleTask@34bb7be0
packetListeners=[PacketAdapter[plugin=Spartan, sending=ListeningWhitelist[priority=NORMAL, packets=[KEEP_ALIVE[class=PacketPlayInKeepAlive, id=16], KEEP_ALIVE[class=PacketPlayOutKeepAlive, id=31], TRANSACTION[class=PacketPlayInTransaction, id=7]], gamephase=PLAYING, options=[]], receiving=ListeningWhitelist[priority=NORMAL, packets=[KEEP_ALIVE[class=PacketPlayInKeepAlive, id=16], KEEP_ALIVE[class=PacketPlayOutKeepAlive, id=31], TRANSACTION[class=PacketPlayInTransaction, id=7]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=VotingPlugin, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[UPDATE_SIGN[class=PacketPlayInUpdateSign, id=43]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=Spartan, sending=EMPTY_WHITELIST, receiving=ListeningWhitelist[priority=NORMAL, packets=[BLOCK_PLACE[class=PacketPlayInBlockPlace, id=47]], gamephase=PLAYING, options=[]]], PacketAdapter[plugin=WildStacker, sending=ListeningWhitelist[priority=NORMAL, packets=[ENTITY_METADATA[class=PacketPlayOutEntityMetadata, id=68]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=HolographicDisplays, sending=ListeningWhitelist[priority=NORMAL, packets=[REL_ENTITY_MOVE_LOOK[class=PacketPlayOutRelEntityMoveLook, id=40], SPAWN_ENTITY[class=PacketPlayOutSpawnEntity, id=0], SPAWN_ENTITY_LIVING[class=PacketPlayOutSpawnEntityLiving, id=2], ENTITY_METADATA[class=PacketPlayOutEntityMetadata, id=68], REL_ENTITY_MOVE[class=PacketPlayOutRelEntityMove, id=39]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST], PacketAdapter[plugin=HolographicExtension, sending=ListeningWhitelist[priority=NORMAL, packets=[ENTITY_METADATA[class=PacketPlayOutEntityMetadata, id=68]], gamephase=PLAYING, options=[]], receiving=EMPTY_WHITELIST]]
packetInjector=com.comphenix.protocol.injector.netty.ProtocolInjector$5@632552
playerInjection=com.comphenix.protocol.injector.netty.ProtocolInjector$4@6268c97c
inputBufferedPackets=[]
recievedListeners=com.comphenix.protocol.injector.SortedPacketListenerList@4935b51a
sendingListeners=com.comphenix.protocol.injector.SortedPacketListenerList@263eb3a7
hasClosed=false
classLoader=PluginClassLoader{plugin=ProtocolLib v4.6.0, pluginEnabled=true, url=plugins/ProtocolLib.jar}
reporter=com.comphenix.protocol.ProtocolLib$1@3f6e5b87
server=CraftServer{serverName=Paper,serverVersion=git-Paper-769,minecraftVersion=1.16.5}
library=ProtocolLib v4.6.0
asyncFilterManager=com.comphenix.protocol.async.AsyncFilterManager@7f90ad2d
knowsServerPackets=true
knowsClientPackets=true
phaseLoginCount=0
phasePlayingCount=8
packetCreation=true
nettyInjector=com.comphenix.protocol.injector.netty.ProtocolInjector@4a159ec3
pluginVerifier=com.comphenix.protocol.injector.PluginVerifier@620a3270
hasRecycleDistance=true
minecraftVersion=(MC: 1.16.5)
debug=false
]
Sender:
com.comphenix.protocol.reflect.compiler.BackgroundCompiler@797a532c[
listeners={com.comphenix.protocol.reflect.compiler.StructureCompiler$StructureKey@e6f59315=[com.comphenix.protocol.injector.StructureCache$1@7c480746]}
listenerLock=java.lang.Object@1acd7d8a
compiler=com.comphenix.protocol.reflect.compiler.StructureCompiler@29674511
enabled=false
shuttingDown=false
executor=java.util.concurrent.Executors$FinalizableDelegatedExecutorService@2af8022
reporter=com.comphenix.protocol.ProtocolLib$1@3f6e5b87
unknownPermGenBean=java.lang.Object@3e61d506
permGenBean=
disablePermGenFraction=0.65
]
Version:
ProtocolLib v4.6.0
Java Version:
16.0.1
Server:
git-Paper-769 (MC: 1.16.5)

Additional context
Add any other context about the problem here.

Try using the latest dev build:
https://ci.dmulloy2.net/job/ProtocolLib/lastSuccessfulBuild/

That solved the same issue for me :)

//edit
ProtocolLib version 4.6.1-SNAPSHOT-b505

thank you it worked, I only have this error in console now, does anyone know what it means

See #1190