ConcurrentModificationException, not sure how to replicate

[robstryker]

java.util.ConcurrentModificationException
at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1230)
at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.pathsAndContainers(JavacFileManager.java:1021)
at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.list(JavacFileManager.java:777)
at jdk.compiler/com.sun.tools.javac.platform.JDKPlatformProvider$PlatformDescriptionImpl$1.list(JDKPlatformProvider.java:188)
at java.compiler@23-ea/javax.tools.ForwardingJavaFileManager.list(ForwardingJavaFileManager.java:82)
at org.eclipse.jdt.internal.javac.CachingJDKPlatformArguments$1$1.list(CachingJDKPlatformArguments.java:123)
at jdk.compiler/com.sun.tools.javac.main.DelegatingJavaFileManager.list(DelegatingJavaFileManager.java:83)
at jdk.compiler/com.sun.tools.javac.code.ClassFinder.list(ClassFinder.java:749)
at jdk.compiler/com.sun.tools.javac.code.ClassFinder.scanModulePaths(ClassFinder.java:621)
at jdk.compiler/com.sun.tools.javac.code.ClassFinder.fillIn(ClassFinder.java:569)
at jdk.compiler/com.sun.tools.javac.code.ClassFinder.complete(ClassFinder.java:311)
at jdk.compiler/com.sun.tools.javac.code.Symbol.complete(Symbol.java:687)
at jdk.compiler/com.sun.tools.javac.code.Symbol$PackageSymbol.members(Symbol.java:1183)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.implicitImports(TypeEnter.java:329)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.resolveImports(TypeEnter.java:381)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.runPhase(TypeEnter.java:318)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.doCompleteEnvs(TypeEnter.java:279)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.completeEnvs(TypeEnter.java:248)
at jdk.compiler/com.sun.tools.javac.comp.TypeEnter.complete(TypeEnter.java:195)
at jdk.compiler/com.sun.tools.javac.code.Symbol.complete(Symbol.java:687)
at jdk.compiler/com.sun.tools.javac.code.Symbol$ClassSymbol.complete(Symbol.java:1455)
at jdk.compiler/com.sun.tools.javac.comp.Enter.complete(Enter.java:632)
at jdk.compiler/com.sun.tools.javac.comp.Enter.main(Enter.java:599)
at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:1077)
at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.enter(JavacTaskImpl.java:345)
at org.eclipse.jdt.core.dom.JavacBindingResolver.resolve(JavacBindingResolver.java:465)
at org.eclipse.jdt.core.dom.JavacBindingResolver.resolvePackage(JavacBindingResolver.java:1236)
at org.eclipse.jdt.core.dom.PackageDeclaration.resolveBinding(PackageDeclaration.java:323)
at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.resolveBindings(JavacCompilationUnitResolver.java:461)
at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.resolveBindings(JavacCompilationUnitResolver.java:455)
at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.toCompilationUnit(JavacCompilationUnitResolver.java:548)
at org.eclipse.jdt.core.dom.ASTParser.internalCreateASTCached(ASTParser.java:1381)
at org.eclipse.jdt.core.dom.ASTParser.lambda$1(ASTParser.java:1260)
at org.eclipse.jdt.internal.core.JavaModelManager.cacheZipFiles(JavaModelManager.java:5708)
at org.eclipse.jdt.core.dom.ASTParser.internalCreateAST(ASTParser.java:1260)
at org.eclipse.jdt.core.dom.ASTParser.createAST(ASTParser.java:915)
at org.eclipse.jdt.core.manipulation.CoreASTProvider$1.run(CoreASTProvider.java:294)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:47)
at org.eclipse.jdt.core.manipulation.CoreASTProvider.createAST(CoreASTProvider.java:286)
at org.eclipse.jdt.core.manipulation.CoreASTProvider.getAST(CoreASTProvider.java:199)
at org.eclipse.jdt.core.manipulation.CoreASTProvider.getAST(CoreASTProvider.java:189)
at org.eclipse.jdt.core.manipulation.CoreASTProvider.getAST(CoreASTProvider.java:189)
at org.eclipse.jdt.core.manipulation.SharedASTProviderCore.getAST(SharedASTProviderCore.java:138)
at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$PartListenerGroup.calculateASTandInform(SelectionListenerWithASTManager.java:167)
at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$PartListenerGroup$1.lambda$0(SelectionListenerWithASTManager.java:149)
at org.eclipse.jdt.internal.core.JavaModelManager.cacheZipFiles(JavaModelManager.java:5708)
at org.eclipse.jdt.internal.core.JavaModelManager.callReadOnly(JavaModelManager.java:5697)
at org.eclipse.jdt.core.JavaCore.callReadOnly(JavaCore.java:6150)
at org.eclipse.jdt.internal.ui.viewsupport.SelectionListenerWithASTManager$PartListenerGroup$1.run(SelectionListenerWithASTManager.java:149)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

[rgrunber]

Ran into this as well :

All I did was open https://github.com/eclipse/lemminx with vscode-java in a workspace that was clean and as the import/build was occuring, I would switch between XMLLanguageServer.java & NoOpPrintStream.java. and scroll around. Given that the errors seem related to code lens handler and inlay hints, it might help to have those options enabled : "java.referencesCodeLens.enabled": true, "java.inlayHints.parameterNames.enabled": "all".

stacktrace1

[Error - 15:48:56] Jan 23, 2025, 3:48:56 p.m. ConcurrentModificationException
null
java.util.ConcurrentModificationException
	at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1230)
	at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.pathsAndContainers(JavacFileManager.java:1021)
	at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.list(JavacFileManager.java:777)
	at jdk.compiler/com.sun.tools.javac.platform.JDKPlatformProvider$PlatformDescriptionImpl$1.list(JDKPlatformProvider.java:188)
	at java.compiler@23/javax.tools.ForwardingJavaFileManager.list(ForwardingJavaFileManager.java:82)
	at org.eclipse.jdt.internal.javac.CachingJDKPlatformArguments$1$1.list(CachingJDKPlatformArguments.java:123)
	at jdk.compiler/com.sun.tools.javac.main.DelegatingJavaFileManager.list(DelegatingJavaFileManager.java:83)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.list(ClassFinder.java:749)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.scanModulePaths(ClassFinder.java:621)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.fillIn(ClassFinder.java:569)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.complete(ClassFinder.java:311)
	at jdk.compiler/com.sun.tools.javac.code.Symbol.complete(Symbol.java:687)
	at jdk.compiler/com.sun.tools.javac.code.Symbol$PackageSymbol.members(Symbol.java:1183)
	at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.implicitImports(TypeEnter.java:329)
	at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.resolveImports(TypeEnter.java:381)
	at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.runPhase(TypeEnter.java:318)
	at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.doCompleteEnvs(TypeEnter.java:279)
	at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.completeEnvs(TypeEnter.java:248)
	at jdk.compiler/com.sun.tools.javac.comp.TypeEnter.complete(TypeEnter.java:195)
	at jdk.compiler/com.sun.tools.javac.code.Symbol.complete(Symbol.java:687)
	at jdk.compiler/com.sun.tools.javac.code.Symbol$ClassSymbol.complete(Symbol.java:1455)
	at jdk.compiler/com.sun.tools.javac.comp.Enter.complete(Enter.java:632)
	at jdk.compiler/com.sun.tools.javac.comp.Enter.main(Enter.java:599)
	at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.enterTrees(JavaCompiler.java:1077)
	at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.enter(JavacTaskImpl.java:345)
	at org.eclipse.jdt.core.dom.JavacBindingResolver.resolve(JavacBindingResolver.java:466)
	at org.eclipse.jdt.core.dom.JavacBindingResolver.resolvePackage(JavacBindingResolver.java:1237)
	at org.eclipse.jdt.core.dom.PackageDeclaration.resolveBinding(PackageDeclaration.java:323)
	at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.resolveBindings(JavacCompilationUnitResolver.java:461)
	at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.resolveBindings(JavacCompilationUnitResolver.java:455)
	at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.toCompilationUnit(JavacCompilationUnitResolver.java:548)
	at org.eclipse.jdt.core.dom.ASTParser.internalCreateASTCached(ASTParser.java:1381)
	at org.eclipse.jdt.core.dom.ASTParser.lambda$1(ASTParser.java:1260)
	at org.eclipse.jdt.internal.core.JavaModelManager.cacheZipFiles(JavaModelManager.java:5708)
	at org.eclipse.jdt.core.dom.ASTParser.internalCreateAST(ASTParser.java:1260)
	at org.eclipse.jdt.core.dom.ASTParser.createAST(ASTParser.java:915)
	at org.eclipse.jdt.internal.core.CompilationUnit.getOrBuildAST(CompilationUnit.java:509)
	at org.eclipse.jdt.internal.codeassist.DOMCodeSelector.codeSelect(DOMCodeSelector.java:63)
	at org.eclipse.jdt.internal.core.CompilationUnit.codeSelect(CompilationUnit.java:487)
	at org.eclipse.jdt.internal.core.CompilationUnit.codeSelect(CompilationUnit.java:479)
	at org.eclipse.jdt.ls.core.internal.JDTUtils.findElementsAtSelection(JDTUtils.java:1069)
	at org.eclipse.jdt.ls.core.internal.JDTUtils.findElementAtSelection(JDTUtils.java:1050)
	at org.eclipse.jdt.ls.core.internal.handlers.CodeLensHandler.resolve(CodeLensHandler.java:98)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$17(JDTLanguageServer.java:813)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:690)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(CompletableFuture.java:527)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:507)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1458)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:2034)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:189)

stacktrace2

[Error - 15:53:41] Jan 23, 2025, 3:53:41 p.m. java.util.ConcurrentModificationException
java.util.ConcurrentModificationException
com.sun.tools.javac.util.ClientCodeException: java.util.ConcurrentModificationException
	at jdk.compiler/com.sun.tools.javac.api.ClientCodeWrapper$WrappedTaskListener.started(ClientCodeWrapper.java:869)
	at jdk.compiler/com.sun.tools.javac.api.MultiTaskListener.started(MultiTaskListener.java:120)
	at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.attribute(JavaCompiler.java:1347)
	at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl$1.process(JavacTaskImpl.java:409)
	at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl$Filter.run(JavacTaskImpl.java:519)
	at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.analyze(JavacTaskImpl.java:412)
	at org.eclipse.jdt.core.dom.JavacBindingResolver.resolve(JavacBindingResolver.java:470)
	at org.eclipse.jdt.core.dom.JavacBindingResolver.resolvePackage(JavacBindingResolver.java:1237)
	at org.eclipse.jdt.core.dom.PackageDeclaration.resolveBinding(PackageDeclaration.java:323)
	at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.resolveBindings(JavacCompilationUnitResolver.java:461)
	at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.resolveBindings(JavacCompilationUnitResolver.java:455)
	at org.eclipse.jdt.core.dom.JavacCompilationUnitResolver.toCompilationUnit(JavacCompilationUnitResolver.java:548)
	at org.eclipse.jdt.core.dom.ASTParser.internalCreateASTCached(ASTParser.java:1381)
	at org.eclipse.jdt.core.dom.ASTParser.lambda$1(ASTParser.java:1260)
	at org.eclipse.jdt.internal.core.JavaModelManager.cacheZipFiles(JavaModelManager.java:5708)
	at org.eclipse.jdt.core.dom.ASTParser.internalCreateAST(ASTParser.java:1260)
	at org.eclipse.jdt.core.dom.ASTParser.createAST(ASTParser.java:915)
	at org.eclipse.jdt.core.manipulation.CoreASTProvider$1.run(CoreASTProvider.java:294)
	at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:47)
	at org.eclipse.jdt.core.manipulation.CoreASTProvider.createAST(CoreASTProvider.java:286)
	at org.eclipse.jdt.core.manipulation.CoreASTProvider.getAST(CoreASTProvider.java:199)
	at org.eclipse.jdt.ls.core.internal.handlers.InlayHintsHandler.inlayHint(InlayHintsHandler.java:59)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$57(JDTLanguageServer.java:1196)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:690)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(CompletableFuture.java:527)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:507)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1458)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:2034)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:189)
Caused by: java.util.ConcurrentModificationException
	at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1230)
	at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.pathsAndContainers(JavacFileManager.java:1021)
	at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.list(JavacFileManager.java:777)
	at jdk.compiler/com.sun.tools.javac.platform.JDKPlatformProvider$PlatformDescriptionImpl$1.list(JDKPlatformProvider.java:188)
	at java.compiler@23/javax.tools.ForwardingJavaFileManager.list(ForwardingJavaFileManager.java:82)
	at org.eclipse.jdt.internal.javac.CachingJDKPlatformArguments$1$1.list(CachingJDKPlatformArguments.java:123)
	at jdk.compiler/com.sun.tools.javac.main.DelegatingJavaFileManager.list(DelegatingJavaFileManager.java:83)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.list(ClassFinder.java:749)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.scanModulePaths(ClassFinder.java:621)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.fillIn(ClassFinder.java:569)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.complete(ClassFinder.java:311)
	at jdk.compiler/com.sun.tools.javac.code.Symbol.complete(Symbol.java:687)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.completeOwners(ClassFinder.java:328)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.complete(ClassFinder.java:296)
	at jdk.compiler/com.sun.tools.javac.code.Symbol.complete(Symbol.java:687)
	at jdk.compiler/com.sun.tools.javac.code.Symbol$ClassSymbol.complete(Symbol.java:1455)
	at jdk.compiler/com.sun.tools.javac.code.ClassFinder.loadClass(ClassFinder.java:446)
	at jdk.compiler/com.sun.tools.javac.comp.Resolve$7.lambda$loadClass$3(Resolve.java:2107)
	at jdk.compiler/com.sun.tools.javac.comp.Resolve.lookupInvisibleSymbol(Resolve.java:2207)
	at jdk.compiler/com.sun.tools.javac.comp.Resolve$7.loadClass(Resolve.java:2100)
	at jdk.compiler/com.sun.tools.javac.comp.Resolve.loadClass(Resolve.java:2081)
	at jdk.compiler/com.sun.tools.javac.comp.Resolve.findIdentInPackageInternal(Resolve.java:2473)
	at jdk.compiler/com.sun.tools.javac.comp.Resolve.findIdentInPackage(Resolve.java:2461)
	at jdk.compiler/com.sun.tools.javac.comp.Attr.selectSym(Attr.java:4541)
	at jdk.compiler/com.sun.tools.javac.comp.Attr.visitSelect(Attr.java:4433)
	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCFieldAccess.accept(JCTree.java:2570)
	at jdk.compiler/com.sun.tools.javac.comp.Attr.attribTree(Attr.java:674)
	at jdk.compiler/com.sun.tools.javac.comp.Attr.attribType(Attr.java:740)
	at jdk.compiler/com.sun.tools.javac.comp.Attr.attribType(Attr.java:733)
	at jdk.compiler/com.sun.tools.javac.api.JavacTrees.attributeDocReference(JavacTrees.java:419)
	at jdk.compiler/com.sun.tools.javac.api.JavacTrees.getElement(JavacTrees.java:345)
	at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitReference(Checker.java:996)
	at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitReference(Checker.java:112)
	at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCReference.accept(DCTree.java:963)
	at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:82)
	at jdk.compiler/com.sun.source.util.DocTreeScanner.visitLink(DocTreeScanner.java:367)
	at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitLink(Checker.java:901)
	at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitLink(Checker.java:112)
	at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCLink.accept(DCTree.java:797)
	at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:82)
	at jdk.compiler/com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:94)
	at jdk.compiler/com.sun.source.util.DocTreeScanner.scan(DocTreeScanner.java:109)
	at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitDocComment(Checker.java:326)
	at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.visitDocComment(Checker.java:112)
	at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCDocComment.accept(DCTree.java:363)
	at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:61)
	at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.scan(Checker.java:320)
	at jdk.javadoc/jdk.javadoc.internal.doclint.Checker.scan(Checker.java:246)
	at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$2.visitDecl(DocLint.java:297)
	at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitClass(DocLint.java:442)
	at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitClass(DocLint.java:425)
	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCClassDecl.accept(JCTree.java:896)
	at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:92)
	at jdk.compiler/com.sun.source.util.TreeScanner.scan(TreeScanner.java:110)
	at jdk.compiler/com.sun.source.util.TreeScanner.scanAndReduce(TreeScanner.java:118)
	at jdk.compiler/com.sun.source.util.TreeScanner.visitCompilationUnit(TreeScanner.java:151)
	at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitCompilationUnit(DocLint.java:469)
	at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$DeclScanner.visitCompilationUnit(DocLint.java:425)
	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCCompilationUnit.accept(JCTree.java:625)
	at jdk.compiler/com.sun.source.util.TreePathScanner.scan(TreePathScanner.java:92)
	at jdk.javadoc/jdk.javadoc.internal.doclint.DocLint$3.started(DocLint.java:308)
	at jdk.compiler/com.sun.tools.javac.api.ClientCodeWrapper$WrappedTaskListener.started(ClientCodeWrapper.java:865)
	... 29 more

[mickaelistria]

I can see it also relatively often (a few times a day when running an IDE using a launch config). Overally, the JavacFileManager isn't really concurrent-friendly. We may need to put some extra synchronization here and there in our custom filemanager.

I suspect this is not the first occurrence of the problem. NetBeans or IntelliJ probably got the same and I'm wondering whether there could be a pre-existing JavacFileManager (with jar caching and so on) we could reuse somewhere...