Package com.puppycrawl.tools.checkstyle.checks.coding

Class WhenShouldBeUsedCheck

java.lang.Object
com.puppycrawl.tools.checkstyle.AbstractAutomaticBean
com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
com.puppycrawl.tools.checkstyle.api.AbstractCheck
com.puppycrawl.tools.checkstyle.checks.coding.WhenShouldBeUsedCheck
All Implemented Interfaces:
Configurable, Contextualizable
public class WhenShouldBeUsedCheck extends AbstractCheck
Ensures that when is used instead of a single if statement inside a case block.

Rationale: Java 21 has introduced enhancements for switch statements and expressions that allow the use of patterns in case labels. The when keyword is used to specify condition for a case label, also called as guarded case labels. This syntax is more readable and concise than the single if statement inside the pattern match block.

See the Java Language Specification for more information about guarded case labels.

See the Java Language Specification for more information about patterns.

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • when.should.be.used
Since:
10.18.0

  • Field Details

  • Constructor Details

  • 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 AbstractCheck
      Parameters:
      ast - the token to process

    • getStatementList

      private static DetailAST getStatementList(DetailAST caseAST)
      Get the statement list token of the case block.
      Parameters:
      caseAST - the AST node representing LITERAL_CASE
      Returns:
      the AST node representing SLIST of the current case

    • getBlockStatements

      private static List<DetailAST> getBlockStatements(DetailAST statementList)
      Get all statements inside the case block.
      Parameters:
      statementList - the AST node representing SLIST of the current case
      Returns:
      statements inside the current case block

    • isAcceptableStatement

      private static boolean isAcceptableStatement(DetailAST ast)
      Check if the statement is an acceptable statement inside the case block. If these statements are the only ones in the case block, this case can be considered a violation. If at least one of the statements is not acceptable, this case can not be a violation.
      Parameters:
      ast - the AST node representing the statement
      Returns:
      true if the statement is an acceptable statement, false otherwise

    • hasPatternLabel

      private static boolean hasPatternLabel(DetailAST caseAST)
      Check if the case block has a pattern variable definition or a record pattern definition.
      Parameters:
      caseAST - the AST node representing LITERAL_CASE
      Returns:
      true if the case block has a pattern label, false otherwise

    • isSingleIfWithNoElse

      private static boolean isSingleIfWithNoElse(DetailAST statement)
      Check if the case block statement is a single if statement with no else branch.
      Parameters:
      statement - statement to check inside the current case block
      Returns:
      true if the statement is a single if statement with no else branch, false otherwise