Package com.puppycrawl.tools.checkstyle.checks.naming

Class PatternVariableNameCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable
    public class PatternVariableNameCheck
extends AbstractNameCheck

    Checks that pattern variable names conform to a specified pattern.

    • Property format - Specifies valid identifiers. Type is java.util.regex.Pattern. Default value is "^[a-z][a-zA-Z0-9]*$".

    To configure the check: 

     <module name="PatternVariableName"/>

    Code Example:

     class MyClass {
     MyClass(Object o1){
         if (o1 instanceof String STRING) { // violation, name 'STRING' must
                                            // match pattern '^[a-z][a-zA-Z0-9]*$'
         }
         if (o1 instanceof Integer num) { // OK
         }
     }
 }

    An example of how to configure the check for names that have a lower case letter, followed by letters and digits, optionally separated by underscore: 

     <module name="PatternVariableName">
   <property name="format" value="^[a-z](_?[a-zA-Z0-9]+)*$"/>
 </module>

    Code Example:

     class MyClass {
     MyClass(Object o1){
         if (o1 instanceof String STR) { // violation, name 'STR' must
                                         // match pattern '^[a-z](_?[a-zA-Z0-9]+)*$'
         }
         if (o1 instanceof Integer num) { // OK
         }
         if (o1 instanceof Integer num_1) { // OK
         }
     }
 }

    An example of how to configure the check to that all variables have 3 or more chars in name: 

     <module name="PatternVariableName">
   <property name="format" value="^[a-z][_a-zA-Z0-9]{2,}$"/>
 </module>

    Code Example:

     class MyClass {
     MyClass(Object o1){
         if (o1 instanceof String s) { // violation, name 's' must
                                       // match pattern '^[a-z][_a-zA-Z0-9]{2,}$'
         }
         if (o1 instanceof Integer num) { // OK
         }
     }
 }

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • name.invalidPattern
    Since:
    8.36

    • Constructor Detail

      • PatternVariableNameCheck

        public PatternVariableNameCheck()
        Creates a new PatternVariableNameCheck instance.

    • Method Detail

      • getDefaultTokens

        public int[] getDefaultTokens()
        Description copied from class: AbstractCheck
        Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.
        Specified by:
        getDefaultTokens in class AbstractCheck
        Returns:
        the default tokens
        See Also:
        TokenTypes

      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Description copied from class: AbstractCheck
        The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
        Specified by:
        getAcceptableTokens in class AbstractCheck
        Returns:
        the token set this check is designed for.
        See Also:
        TokenTypes

      • getRequiredTokens

        public int[] getRequiredTokens()
        Description copied from class: AbstractCheck
        The tokens that this check must be registered for.
        Specified by:
        getRequiredTokens in class AbstractCheck
        Returns:
        the token set this must be registered for.
        See Also:
        TokenTypes

      • mustCheckName

        protected final boolean mustCheckName​(DetailAST ast)
        Description copied from class: AbstractNameCheck
        Decides whether the name of an AST should be checked against the format regexp.
        Specified by:
        mustCheckName in class AbstractNameCheck
        Parameters:
        ast - the AST to check.
        Returns:
        true if the IDENT subnode of ast should be checked against the format regexp.