Checkstyle Nullability Annotations

A custom check for Checkstyle that ensures that field, method parameter and return types are annotated with annotations specified in the check's configuration.

At the moment, check doesn't recognize annotations specified at the class level.

Supported tokens

• CTOR_DEF for checking constructor parameter types
• METHOD_DEF for checking method parameter and return types
• VARIABLE_DEF for checking non-local field types

Supported properties

Name	Type	Default	Description
tokens	String[]	CTOR_DEF, METHOD_DEF, VARIABLE_DEF	Any combination of tokens above
nonnullClassNames	String[]	Not specified, mandatory	Fully qualified class names that should be treated as "Nonnull" annotations.
nullableClassNames	String[]	Not specified, mandatory	Fully qualified class names that should be treated as "Nullable" annotations.
checkLocalVariables	boolean	true	Whether local variables should be checked as well

Sample module configuration

<module name="NullabilityAnnotationsCheck">
    <property name="tokens" value="CTOR_DEF, METHOD_DEF, VARIABLE_DEF"/>
    <property name="nonnullClassNames" value="org.jspecify.annotations.NonNull"/>
    <property name="nullableClassNames" value="org.jspecify.annotations.Nullable"/>
    <property name="checkLocalVariables" value="false"/>
</module>