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

Class FinalPatternVariableCheck

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.FinalPatternVariableCheck
All Implemented Interfaces:
Configurable, Contextualizable
public class FinalPatternVariableCheck extends AbstractCheck
Checks that pattern variables that never have their values changed are declared final.

Pattern variables are not implicitly final in Java, and they can be reassigned. This check verifies that pattern variables are explicitly declared as final if they are not reassigned within their flow scope.

Since:
14.4.0

  • Field Details

  • Constructor Details

  • Method Details

    • 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:

    • 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:

    • 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

    • getPatternVariableIdents

      private static List<DetailAST> getPatternVariableIdents(DetailAST ast)
      Gets the list of all pattern variable idents in instanceof expression.
      Parameters:
      ast - ast tree of instanceof to get the list from.
      Returns:
      list of pattern variables.

    • collectRecordPatternIdents

      private static void collectRecordPatternIdents(DetailAST recordPatternDef, Collection<DetailAST> patternVariableIdentsArray)
      Collects pattern variable identifiers from a record pattern AST definition.
      Parameters:
      recordPatternDef - AST of record pattern definition
      patternVariableIdentsArray - collection to add pattern variable identifiers to

    • getReassignedVariableIdents

      private static List<DetailAST> getReassignedVariableIdents(DetailAST ast)
      Gets the list of AST branches of reassigned variable identifiers.
      Parameters:
      ast - ast tree of checked instanceof statement
      Returns:
      list of AST identifiers that represent reassigned variables

    • getStatementsInExtendedScope

      private static List<DetailAST> getStatementsInExtendedScope(DetailAST conditionalStatement)
      Gets statements that follow conditional where pattern variable scope extends. Only returns top-level statements that are siblings of the conditional, excluding statements nested in control structures like while loops.
      Parameters:
      conditionalStatement - The if statement.
      Returns:
      List of statement nodes in the extended scope.

    • shiftToNextTraversedBranch

      @Nullable private static DetailAST shiftToNextTraversedBranch(DetailAST ast, DetailAST boundAst)
      Shifts once to the next possible branch within traverse trajectory.
      Parameters:
      ast - AST branch to shift from.
      boundAst - AST Branch that traverse cannot extend to.
      Returns:
      next possible branch within traverse trajectory.

    • getMatchedAssignToken

      @Nullable private static DetailAST getMatchedAssignToken(DetailAST preAssignBranch)
      Gets the type of ASSIGN tokens that matches with what follows the preceding branch.
      Parameters:
      preAssignBranch - branch preceding ASSIGN token types.
      Returns:
      type of ASSIGN token.

    • shouldBeFinal

      private static boolean shouldBeFinal(DetailAST patternVariableIdent, Iterable<DetailAST> reassignedVariableIdents)
      Checks whether a pattern variable should be declared final.
      Parameters:
      patternVariableIdent - AST ident of the pattern variable
      reassignedVariableIdents - list of AST idents of reassigned vars
      Returns:
      true if pattern variable should be final, false otherwise

    • findReassignmentScopeRoot

      @Nullable private static DetailAST findReassignmentScopeRoot(DetailAST ast)
      Finds the nearest AST node that defines the scope in which reassignment of a pattern variable may occur.

      The scope is determined by locating the closest enclosing conditional structure such as if, else, or ternary operator.

      Parameters:
      ast - the AST node to start searching from
      Returns:
      the AST node representing the reassignment scope root, or null if none is found

    • expandReassignmentScopes

      private static List<DetailAST> expandReassignmentScopes(DetailAST scopeRoot)
      Expands the reassignment scope root into concrete AST branches that may contain reassigned pattern variables.

      For ternary expressions, the conditional expression itself is treated as the reassignment scope. For if / else statements, the method includes the statement list and any subsequent statements where the pattern variable remains in scope.

      Parameters:
      scopeRoot - the root AST node of the reassignment scope
      Returns:
      list of AST branches that may contain reassignments

    • addBodyBranch

      private static void addBodyBranch(Collection<DetailAST> branches, DetailAST scopeRoot)
      Adds the body branch of a conditional (if/else) to the list. For braced blocks, adds the SLIST. For unbraced statements, adds the single statement directly.
      Parameters:
      branches - collection to add the body branch to
      scopeRoot - the if/else AST node