No auto-completion, no marking of compilation errors, etc.

[anthonyvdotbe]

I've done Clean Java Language Server Workspace, activated the "heavyweight mode" and waited for Java: Ready, but the extension still barely offers any support. Stack traces from the logs:

[Error - 11:33:40 AM] Request textDocument/codeAction failed.
  Message: Internal error.
  Code: -32603 
java.util.concurrent.CompletionException: java.lang.NullPointerException: Cannot invoke "org.eclipse.jdt.core.IMethod.getCompilationUnit()" because "iMethod" is null
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.scan(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
Caused by: java.lang.NullPointerException: Cannot invoke "org.eclipse.jdt.core.IMethod.getCompilationUnit()" because "iMethod" is null
	at org.eclipse.jdt.internal.corext.refactoring.code.makestatic.InitialConditionsChecker.checkSourceAvailable(InitialConditionsChecker.java:181)
	at org.eclipse.jdt.internal.corext.refactoring.code.MakeStaticRefactoring.checkInitialConditions(MakeStaticRefactoring.java:127)
	at org.eclipse.jdt.ls.core.internal.corrections.RefactorProcessor.getMakeMethodStaticRefactoringProposal(RefactorProcessor.java:1189)
	at org.eclipse.jdt.ls.core.internal.corrections.RefactorProcessor.getProposals(RefactorProcessor.java:228)
	at org.eclipse.jdt.ls.core.internal.handlers.CodeActionHandler.getCodeActionCommands(CodeActionHandler.java:221)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$15(JDTLanguageServer.java:775)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	... 7 more

java.util.concurrent.CompletionException: java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 1
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.scan(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
Caused by: java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 1
	at org.eclipse.jdt.internal.corext.fix.AddMissingMethodDeclarationFixCore$AddMissingMethodDeclarationProposalOperation.rewriteAST(AddMissingMethodDeclarationFixCore.java:241)
	at org.eclipse.jdt.internal.corext.fix.CompilationUnitRewriteOperationsFixCore.createChange(CompilationUnitRewriteOperationsFixCore.java:123)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getAddMissingMethodDeclarationProposal(QuickAssistProcessor.java:1459)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getAssists(QuickAssistProcessor.java:237)
	at org.eclipse.jdt.ls.core.internal.handlers.CodeActionHandler.getCodeActionCommands(CodeActionHandler.java:233)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$15(JDTLanguageServer.java:775)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	... 7 more

SEVERE: Internal error: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
java.util.concurrent.CompletionException: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.scan(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
Caused by: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
	at java.base/jdk.internal.util.Preconditions.outOfBounds(Unknown Source)
	at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Unknown Source)
	at java.base/jdk.internal.util.Preconditions.checkIndex(Unknown Source)
	at java.base/java.util.Objects.checkIndex(Unknown Source)
	at java.base/java.util.ArrayList.get(Unknown Source)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getTryWithResourceProposals(QuickAssistProcessor.java:1014)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getTryWithResourceProposals(QuickAssistProcessor.java:936)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getAssists(QuickAssistProcessor.java:238)
	at org.eclipse.jdt.ls.core.internal.handlers.CodeActionHandler.getCodeActionCommands(CodeActionHandler.java:233)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$15(JDTLanguageServer.java:775)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	... 7 more

pre-release extension version 1.43.2025061908

Version: 1.101.1 (user setup)
Commit: 18e3a1ec544e6907be1e944a94c496e302073435
Date: 2025-06-18T13:35:12.605Z
Electron: 35.5.1
ElectronBuildId: 11727614
Chromium: 134.0.6998.205
Node.js: 22.15.1
V8: 13.4.114.21-electron.0
OS: Windows_NT x64 10.0.22631

[rgrunber]

Are there any major errors at all reported in the problems view ? Would you be able to share the project, or even a sample of code where these errors are occuring ? They appear to be code actions so they're likely associated with a particular line of code. Also, does your project use Lombok ?

[anthonyvdotbe]

The issue was transient, eventually things were working as expected again. I don't remember whether there were errors in the problems view. There were definitely compilation errors in the project (I actually ran a Maven build outside VS Code to convince myself of that), but the editor didn't show any of them. And when trying to autocomplete, I only got the dreaded No suggestions. The project is not using Lombok. Sharing the project as a whole is not an option, since it's owned by my employer. That being said: I'd consider the projects I'm working on pretty basic: Spring Boot web services, some tooling/glue, etc.

Feel free to close the issue if you consider the stack traces are not actionable on themselves.

[anthonyvdotbe]

So today I wanted to work on a Spring Boot project (the status was Java: Ready): I open up a file and start typing. I immediately get the following 2 errors showing up. To try and be efficient, I copy the System.out.println(...); line and want to paste it a couple times. However, on each and every single paste, I run into #3936 (final image below).
I'm really trying to like Java in VS Code, but this extension just contains so many small bugs like this, that it makes for a very frustrating experience. Oracle's extension is better in this regard (I assume this one will also be once it makes javac the default), but lacks some essential features, like the ability to auto-import types on "Organize Imports".

[phabreeze]

I ran into this exact issue yesterday, no IntelliSense, no errors, the project wasn’t recognized as a Java project, and unit tests wouldn’t show up.

After spending half a day troubleshooting on my mac, I found a workaround that got everything working. It might not be the root cause fix, but here’s what worked for me:

1. Added maven-eclipse-plugin plugin to pom.xml

    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-eclipse-plugin</artifactId>
        <version>2.10</version>
    </plugin>

2. Ran mvn eclipse:eclipse in the root folder to generate .project and .classpath files.
3. Uninstalled the Test Runner for Java and Debugger for Java extensions (if installed).
4. Restarted VS Code.
5. Reinstalled those two extensions.

After that, everything started working again like magic.

[taliamccormick]

Workaround of installing Maven + disabling the "Test Runner for Java" extension seems to have worked for me -- thanks