Version 4.3.0 (2026-10-01)

User-visible changes

The new Modifiability Checker warns when a program might throw UnsupportedOperationException at run time because it calls a mutating method on a collection that does not support the method.

The new wpi2.sh script does whole-program inference, but requires buildfile edits.

Purity Checker:

• Renamed message keys purity.not.deterministic.X, purity.not.sideeffectfree.X, and purity.not.deterministic.not.sideeffectfree.X to purity.X.
• -AcheckPurityAnnotations issues warnings that it missed previously.

The Checker Framework runs under JDK 27 -- that is, it runs on a version 27 JVM.

The Checker Framework runs noticeably faster, due to performance tuning.

The HTML version of the manual has a new look. In addition to the single-page version, there is a multi-page version.

Changes for type system implementers

JavaParserUtil: moved DEFAULT_LANGUAGE_LEVEL, parseCompilationUnit(), parseStubUnit(), and parseExpression() into new class StaticJavaParserUtil.

Renamed AnnotatedTypes.innerMostType() to innermostComponentType().

Removed the unused method
WholeProgramInferenceScenesStorage.updateAnnotationSetInScene().

Methods that used to return (or accept) an IPair now use a record with meaningful component names.

Closed issues

#294, #1170, #1184, #1256, #1440, #1444, #1669, #2090, #2172, #2429, #2448, #2561, #2637, #2704, #2722, #2770, #2896, #2995, #3015, #3025, #3027, #3146, #3281, #3624, #4690, #4708, #4754, #5064, #5201, #6038, #6716, #6741, #6748, #6756, #6768, #6832, #6881, #7023, #7049, #7064, #7311, #7683, #8053, #8054, #8055, #8167, #8168, #8169, #8238, #8261, #8284.

Version 4.2.3 (2026-09-01)

User-visible changes

The -AsuggestPureMethods command-line option and the purity.effectively.pure warning no longer require -AcheckPurityAnnotations to also be supplied.

Implementation details

Made the field Java8InferenceContext.pathToExpression private; use getPathToExpression() and setPathToExpression() instead.

Renamed TreeUtils.isLikeDiamondMemberReference() to isRawTypedMemberReference().

Closed issues

#2816, #7677, #7678, #7681, #7682, #7684, #7693, #7694, #7696, #7698, #7701, #7702, #7875, #8046, #8047, #8048, #8050, #8052.

Version 4.2.2 (2026-08-06)

Implementation details

Renamed CFAbstractValue.validateSet() to hasAnnotationFromEveryHierarchy().

Closed issues

#7723, #7784, #7806.

Version 4.2.1 (2026-07-01)

Closed issues

#7726.

Version 4.2.0 (2026-06-01)

User-visible changes

Renamed error message key "createsmustcallfor.target.unparseable" to "createsmustcallfor.target.unparsable".

Implementation details

In AnnotatedTypeFactory:

• new overload canonicalAnnotation(AnnotationMirror, TypeMirror).

In TypeHierarchy:

• new methods equalsShallowEffective().

Closed issues

#7676, #7679, #7680, #7695, #7697, #7699, #7700, #7727.

Version 4.1.0 (2026-05-01)

User-visible changes

Removed deprecated script checker/bin-devel/build.sh; use ./gradlew assemble instead.

Removed deprecated names "builder", "object.construction", and "objectconstruction" for the Called Methods Checker.

Implementation details

New method annotation @DoesNotUnrefineReceiver.

In AnnotatedTypeFactory:

• new method hasDoesNotUnrefineReceiver().
• isAliasedTypeAnnotation() is now protected rather than public.

Closed issues

#6890, #7364, #7488.

Version 4.0.0 (2026-04-07)

User-visible changes

To run the Checker Framework, you need to use a JDK 17 or later version of javac. That is, you need to use JDK 17 or later when compiling your code.

The Checker Framework can type-check any Java project, including projects that compile to Java 8 or 11 bytecodes and run on JRE versions 8 or 11. That is, your code can run under any release of Java, from Java 8 onward.

The type qualifiers and utility libraries in checker-qual.jar and checker-util.jar still use Java 11 bytecode. Thus, they may be used in projects that run under Java 11 or later.

Changes since version 3.0.0

Since version 3.0.0, 91 authors have made over 4500 commits and closed over 600 issues. Thanks to everyone who contributed!

New checkers include:

• The Index Checker warns about out-of-bounds accesses to arrays and strings.
• The Initialized Fields Checker warns if a constructor does not initialize a field.
• The Resource Leak Checker guarantees that every resource is closed rather than leaked. Examples of resources are a channel, executor, ExecutionControl, file, FileLock, Formatter, reader, Scanner, socket, stream, writer, etc.
• The SQL Quotes Checker helps prevent SQL injection vulnerabilities.

New command-line arguments include:

• -AskipFiles, -AonlyFiles
• -AassumeSideEffectFree, -AassumeDeterministic, -AassumePure, -AassumePureGetters
• -AuseConservativeDefaultsForUncheckedCode
• -AignoreRawTypeArguments
• -AwarnRedundantAnnotations
• -Ainfer=ajava, -AinferOutputDirectory, -AinferOutputOriginal, -AshowWpiFailedInferences
• -AshowSuppressWarningsStrings, -AwarnUnneededSuppressionsExceptions
• -AshowPrefixInWarningMessages
• -AstubNoWarnIfNotFound, -AstubWarnNote, -AmergeStubsWithSource
• -Aonelinemsg, -AdumpOnErrors, -AexceptionLineSeparator
• -ApermitMissingJdk, -AparseAllJdk
• -AslowTypecheckingSeconds
• -Aversion, -AprintGitProperties
• You can pass an option to only a particular checker (not all checkers) by using an underscore prefix.

Other improvements include thousands of enhancements and bug fixes -- too many to list here.

Implementation details

All previously-deprecated methods and classes have been removed. If your project builds upon the Checker Framework, we suggest that you upgrade to version 3.55.1, resolve all the deprecation warnings, then upgrade to version 4.0.0.

Version 3.55.1 (2026-04-03)

No user-visible changes.

Version 3.55.0 (2026-04-02)

User-visible changes

The Checker Framework runs under JDK 26 -- that is, it runs on a version 26 JVM.

Removed deprecated command-line option -AskipDirs; use -AskipFiles.

Implementation details

In AnnotatedTypeMirror:

• Renamed getEffectiveAnnotation*() to getAnnotation*().
• Renamed hasEffectiveAnnotation*() to hasAnnotation*().

Removed deprecated method ObjectCreationNode.getConstructor(); use
getTypeToInstantiate().

Closed issues

#7079, #7489, #7539.

Version 3.54.0 (2026-03-02)

User-visible changes

Command-line arguments:

• Added -AinferOutputDirectory.
• Removed long-deprecated -Alint=forbidnonnullarraycomponents.

New command-line argument -Aonelinemsg puts error messages on a single line. This is useful when using a tool that only shows the first line of the error.

The command-line argument -Anomsgtext surrounds the error key with brackets instead of parenthesis. This matches Java error messages.

Implementation details

In AnnotatedTypeFactory, canonicalAnnotation() returns a non-null value.

In AnnotationClassLoader:

• Renamed hasWellDefinedTargetMetaAnnotation() to isTypeQualifierAnnotation(). The method now returns true for annotations bearing @InvisibleQualifier or @SubtypeOf, in addition to the existing @Target(TYPE_USE) check.

In TestDiagnostic:

• Renamed field message to key.
• Added new nullable field message for the full message without the key.

Removed classes and methods that have been deprecated for more than two years.

Closed issues

#6874, #7471, #7475, #7486.