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

Class FinalLocalVariableCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable
    public class FinalLocalVariableCheck
extends AbstractCheck

    Checks that local variables that never have their values changed are declared final. The check can be configured to also check that unchanged parameters are declared final.

    When configured to check parameters, the check ignores parameters of interface methods and abstract methods.

    • Property validateEnhancedForLoopVariable - Control whether to check enhanced for-loop variable. Type is boolean. Default value is false.
    • Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: VARIABLE_DEF.

    To configure the check: 

     <module name="FinalLocalVariable"/>

    To configure the check so that it checks local variables and parameters: 

     <module name="FinalLocalVariable">
   <property name="tokens" value="VARIABLE_DEF,PARAMETER_DEF"/>
 </module>

    By default, this Check skip final validation on Enhanced For-Loop.

    Option 'validateEnhancedForLoopVariable' could be used to make Check to validate even variable from Enhanced For Loop.

    An example of how to configure the check so that it also validates enhanced For Loop Variable is: 

     <module name="FinalLocalVariable">
   <property name="tokens" value="VARIABLE_DEF"/>
   <property name="validateEnhancedForLoopVariable" value="true"/>
 </module>

    Example:

     for (int number : myNumbers) { // violation
   System.out.println(number);
 }

    An example of how to configure check on local variables and parameters but do not validate loop variables: 

     <module name="FinalLocalVariable">
    <property name="tokens" value="VARIABLE_DEF,PARAMETER_DEF"/>
    <property name="validateEnhancedForLoopVariable" value="false"/>
  </module>

    Example: 

     public class MyClass {
   static int foo(int x, int y) { //violations, parameters should be final
     return x+y;
   }
   public static void main (String []args) { //violation, parameters should be final
     for (String i : args) {
       System.out.println(i);
     }
     int result=foo(1,2); // violation
   }
 }

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • final.variable
    Since:
    3.2

    • Method Detail

      • setValidateEnhancedForLoopVariable

        public final void setValidateEnhancedForLoopVariable​(boolean validateEnhancedForLoopVariable)
        Setter to control whether to check enhanced for-loop variable.
        Parameters:
        validateEnhancedForLoopVariable - whether to check for-loop variable

      • 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

      • isInSpecificCodeBlocks

        private static boolean isInSpecificCodeBlocks​(DetailAST node,
                                              int... blockTypes)
        Checks whether the scope of a node is restricted to a specific code blocks.
        Parameters:
        node - node.
        blockTypes - int array of all block types to check.
        Returns:
        true if the scope of a node is restricted to specific code block types.

      • updateAllUninitializedVariables

        private void updateAllUninitializedVariables​(java.util.Deque<DetailAST> prevScopeUninitializedVariableData)
        Update current scope data uninitialized variable according to the whole scope data.
        Parameters:
        prevScopeUninitializedVariableData - variable for previous stack of uninitialized variables

      • updateUninitializedVariables

        private void updateUninitializedVariables​(java.util.Deque<DetailAST> scopeUninitializedVariableData)
        Update current scope data uninitialized variable according to the specific scope data.
        Parameters:
        scopeUninitializedVariableData - variable for specific stack of uninitialized variables

      • shouldUpdateUninitializedVariables

        private static boolean shouldUpdateUninitializedVariables​(DetailAST ast)
        If token is LITERAL_IF and there is an else following or token is CASE_GROUP or SWITCH_RULE and there is another case following, then update the uninitialized variables.
        Parameters:
        ast - token to be checked
        Returns:
        true if should be updated, else false

      • isIfTokenWithAnElseFollowing

        private static boolean isIfTokenWithAnElseFollowing​(DetailAST ast)
        If token is LITERAL_IF and there is an else following.
        Parameters:
        ast - token to be checked
        Returns:
        true if token is LITERAL_IF and there is an else following, else false

      • isCaseTokenWithAnotherCaseFollowing

        private static boolean isCaseTokenWithAnotherCaseFollowing​(DetailAST ast)
        If token is CASE_GROUP or SWITCH_RULE and there is another case following.
        Parameters:
        ast - token to be checked
        Returns:
        true if token is CASE_GROUP or SWITCH_RULE and there is another case following, else false

      • findLastChildWhichContainsSpecifiedToken

        private static DetailAST findLastChildWhichContainsSpecifiedToken​(DetailAST ast,
                                                                  int childType,
                                                                  int containType)
        Returns the last child token that makes a specified type and contains containType in its branch.
        Parameters:
        ast - token to be tested
        childType - the token type to match
        containType - the token type which has to be present in the branch
        Returns:
        the matching token, or null if no match

      • shouldCheckEnhancedForLoopVariable

        private boolean shouldCheckEnhancedForLoopVariable​(DetailAST ast)
        Determines whether enhanced for-loop variable should be checked or not.
        Parameters:
        ast - The ast to compare.
        Returns:
        true if enhanced for-loop variable should be checked.

      • insertParameter

        private void insertParameter​(DetailAST ast)
        Insert a parameter at the topmost scope stack.
        Parameters:
        ast - the variable to insert.

      • insertVariable

        private void insertVariable​(DetailAST ast)
        Insert a variable at the topmost scope stack.
        Parameters:
        ast - the variable to insert.

      • isInitialized

        private static boolean isInitialized​(DetailAST ast)
        Check if VARIABLE_DEF is initialized or not.
        Parameters:
        ast - VARIABLE_DEF to be checked
        Returns:
        true if initialized

      • isFirstChild

        private static boolean isFirstChild​(DetailAST ast)
        Whether the ast is the first child of its parent.
        Parameters:
        ast - the ast to check.
        Returns:
        true if the ast is the first child of its parent.

      • isMultipleTypeCatch

        private static boolean isMultipleTypeCatch​(DetailAST parameterDefAst)
        Check if given parameter definition is a multiple type catch.
        Parameters:
        parameterDefAst - parameter definition
        Returns:
        true if it is a multiple type catch, false otherwise

      • shouldRemoveFinalVariableCandidate

        private static boolean shouldRemoveFinalVariableCandidate​(FinalLocalVariableCheck.ScopeData scopeData,
                                                          DetailAST ast)
        Whether the final variable candidate should be removed from the list of final local variable candidates.
        Parameters:
        scopeData - the scope data of the variable.
        ast - the variable ast.
        Returns:
        true, if the variable should be removed.

      • isUseOfExternalVariableInsideLoop

        private static boolean isUseOfExternalVariableInsideLoop​(DetailAST variable)
        Checks whether a variable which is declared outside loop is used inside loop. For example:

        int x; for (int i = 0, j = 0; i < j; i++) { x = 5; }

        Parameters:
        variable - variable.
        Returns:
        true if a variable which is declared outside loop is used inside loop.

      • isAssignOperator

        private static boolean isAssignOperator​(int parentType)
        Is Arithmetic operator.
        Parameters:
        parentType - token AST
        Returns:
        true is token type is in arithmetic operator

      • isVariableInForInit

        private static boolean isVariableInForInit​(DetailAST variableDef)
        Checks if current variable is defined in for-loop init, e.g.:

        for (int i = 0, j = 0; i < j; i++) { . . . }

        i, j are defined in for-loop init
        Parameters:
        variableDef - variable definition node.
        Returns:
        true if variable is defined in for-loop init

      • isInAbstractOrNativeMethod

        private static boolean isInAbstractOrNativeMethod​(DetailAST ast)
        Determines whether an AST is a descendant of an abstract or native method.
        Parameters:
        ast - the AST to check.
        Returns:
        true if ast is a descendant of an abstract or native method.

      • isInLambda

        private static boolean isInLambda​(DetailAST paramDef)
        Check if current param is lambda's param.
        Parameters:
        paramDef - parameter def.
        Returns:
        true if current param is lambda's param.

      • findFirstUpperNamedBlock

        private static DetailAST findFirstUpperNamedBlock​(DetailAST ast)
        Find the Class, Constructor, Enum, Method, or Field in which it is defined.
        Parameters:
        ast - Variable for which we want to find the scope in which it is defined
        Returns:
        ast The Class or Constructor or Method in which it is defined.

      • isSameVariables

        private static boolean isSameVariables​(DetailAST ast1,
                                       DetailAST ast2)
        Check if both the Variables are same.
        Parameters:
        ast1 - Variable to compare
        ast2 - Variable to compare
        Returns:
        true if both the variables are same, otherwise false

      • isInTheSameLoop

        private static boolean isInTheSameLoop​(DetailAST ast1,
                                       DetailAST ast2)
        Check if both the variables are in the same loop.
        Parameters:
        ast1 - variable to compare.
        ast2 - variable to compare.
        Returns:
        true if both the variables are in the same loop.

      • isLoopAst

        private static boolean isLoopAst​(int ast)
        Checks whether the ast is a loop.
        Parameters:
        ast - the ast to check.
        Returns:
        true if the ast is a loop.