Class LambdaParameterNameCheck

java.lang.Object
com.puppycrawl.tools.checkstyle.api.AutomaticBean
com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
com.puppycrawl.tools.checkstyle.api.AbstractCheck
com.puppycrawl.tools.checkstyle.checks.naming.AbstractNameCheck
com.puppycrawl.tools.checkstyle.checks.naming.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 Details

    • LambdaParameterNameCheck

      public LambdaParameterNameCheck()
      Creates new instance of LambdaParameterNameCheck.

  • Method Details

    • 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:

    • 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:

    • 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:

    • visitToken

      public void visitToken(DetailAST ast)
      Description copied from class: AbstractCheck
      Called to process a token.
      Overrides:
      visitToken in class AbstractNameCheck
      Parameters:
      ast - the token to process

    • 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.