Since Checkstyle 8.36
Checks identifiers with a pattern for a set of illegal names, such as those that are restricted or contextual keywords. Examples include "yield", "record", "_", and "var". Please read more at Java Language Specification to get to know more about restricted keywords. Since this check uses a pattern to specify valid identifiers, users can also prohibit the usage of certain symbols, such as "$", or any non-ascii character.
name | description | type | default value | since |
---|---|---|---|---|
format | Specifies valid identifiers. | Pattern |
"(?i)^(?!(record|yield|var|permits|sealed|_)$).+$"
|
8.36 |
tokens | tokens to check | subset of tokens CLASS_DEF , INTERFACE_DEF , ENUM_DEF , ANNOTATION_DEF , ANNOTATION_FIELD_DEF , PARAMETER_DEF , VARIABLE_DEF , METHOD_DEF , ENUM_CONSTANT_DEF , PATTERN_VARIABLE_DEF , RECORD_DEF , RECORD_COMPONENT_DEF , LAMBDA . | CLASS_DEF , INTERFACE_DEF , ENUM_DEF , ANNOTATION_DEF , ANNOTATION_FIELD_DEF , PARAMETER_DEF , VARIABLE_DEF , METHOD_DEF , ENUM_CONSTANT_DEF , PATTERN_VARIABLE_DEF , RECORD_DEF , RECORD_COMPONENT_DEF , LAMBDA . | 8.36 |
To configure the check:
Configuration:
<module name="Checker"> <module name="TreeWalker"> <module name="IllegalIdentifierName"/> </module> </module>
Example:
public class TestClass { public static void main(String... args) { var var = 4; // violation, "var" should not be used as an identifier. int record = 15; // violation, "record" should not be used as an identifier. String yield = "yield"; // violation, "yield" should not be used as an identifier. record Record // violation, "Record" should not be used as an identifier. (Record record) { // violation, "record" should not be used as an identifier. } String yieldString = "yieldString"; // ok, part of another word record MyRecord(){} // ok, part of another word var variable = 2; // ok, part of another word String _; // violation, underscore should not be used as an identifier. } }
To configure the check to include "open" and "transitive" in the set of illegal identifiers:
Configuration:
<module name="Checker"> <module name="TreeWalker"> <module name="IllegalIdentifierName"> <property name="format" value="(?i)^(?!(record|yield|var |permits|sealed|open|transitive|_)$).+$"/> </module> </module> </module>
Example:
public class TestClass { public static void main(String... args) { int open = 4; // violation, "open" should not be used as an identifier Object transitive = "transitive"; // violation, "transitive" should not // be used as an identifier int openInt = 4; // ok, "open" is part of another word Object transitiveObject = "transitiveObject"; // ok, "transitive" is part of another word } }
All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.
com.puppycrawl.tools.checkstyle.checks.naming