Class IllegalIdentifierNameCheck

Checks identifiers with a regular expression 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 regular expression to specify valid identifiers, users can also prohibit the usage of certain symbols, such as "$", or any non-ascii character.

• Property format - Specifies valid identifiers. Type is java.util.regex.Pattern. Default value is "(?i)^(?!(record|yield|var|permits|sealed|_)$).+$".
• Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: 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.

To configure the check:

Configuration:

 <module name="IllegalIdentifierName"/>
 

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="IllegalIdentifierName">
     <property name="format" value="(?i)^(?!(record|yield|var
                        |permits|sealed|open|transitive|_)$).+$"/>
 </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
     }
 }
 

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• name.invalidPattern