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

Class LambdaParameterNameCheck

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

    Checks lambda parameter names.

    • 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="LambdaParameterName"/>

    Code Example:

     Function<String, String> function1 = s -> s.toLowerCase(); // OK
 Function<String, String> function2 = S -> S.toLowerCase(); // violation, name 'S'
                                                // must match pattern '^[a-z][a-zA-Z0-9]*$'

    An example of how to configure the check for names that begin with a lower case letter, followed by letters is: 

     <module name="LambdaParameterName">
   <property name="format" value="^[a-z]([a-zA-Z]+)*$"/>
 </module>

    Code Example: 

     class MyClass {
   Function<String, String> function1 = str -> str.toUpperCase().trim(); // OK
   Function<String, String> function2 = _s -> _s.trim(); // violation, name '_s'
                                              // must match pattern '^[a-z]([a-zA-Z]+)*$'

   public boolean myMethod(String sentence) {
     return Stream.of(sentence.split(" "))
             .map(word -> word.trim()) // OK
             .anyMatch(Word -> "in".equals(Word)); // violation, name 'Word'
                                                      // must match pattern '^[a-z]([a-zA-Z]+)*$'
   }
 }

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • name.invalidPattern
    Since:
    8.11

    • Constructor Detail

      • LambdaParameterNameCheck

        public LambdaParameterNameCheck()
        Creates new instance of LambdaParameterNameCheck.

    • 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 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.