IllegalIdentifierName

Since Checkstyle 8.36

Description

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.

Properties

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

Examples

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
    }
}

Example of Usage

Violation Messages

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Package

com.puppycrawl.tools.checkstyle.checks.naming

Parent Module

TreeWalker