Class ParameterAssignmentCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public final class ParameterAssignmentCheck
    extends AbstractCheck

    Disallows assignment of parameters.

    Rationale: Parameter assignment is often considered poor programming practice. Forcing developers to declare parameters as final is often onerous. Having a check ensure that parameters are never assigned would give the best of both worlds.

    To configure the check:

     <module name="ParameterAssignment"/>
     

    Example:

     class MyClass {
       int methodOne(int parameter) {
         if (parameter <= 0 ) {
           throw new IllegalArgumentException("A positive value is expected");
         }
         parameter -= 2;  // violation
         return parameter;
       }
    
       int methodTwo(int parameter) {
         if (parameter <= 0 ) {
           throw new IllegalArgumentException("A positive value is expected");
         }
         int local = parameter;
         local -= 2;  // OK
         return local;
       }
    
       IntPredicate obj = a -> ++a == 12; // violation
       IntBinaryOperator obj2 = (int a, int b) -> {
           a++;     // violation
           b += 12; // violation
           return a + b;
       };
       IntPredicate obj3 = a -> {
           int b = a; // ok
           return ++b == 12;
       };
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • parameter.assignment
    Since:
    3.2
    • Field Detail

      • MSG_KEY

        public static final java.lang.String MSG_KEY
        A key is pointing to the warning message text in "messages.properties" file.
        See Also:
        Constant Field Values
      • parameterNamesStack

        private final java.util.Deque<java.util.Set<java.lang.String>> parameterNamesStack
        Stack of methods' parameters.
      • parameterNames

        private java.util.Set<java.lang.String> parameterNames
        Current set of parameters.
    • Constructor Detail

      • ParameterAssignmentCheck

        public ParameterAssignmentCheck()
    • 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
      • 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
      • 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
      • beginTree

        public void beginTree​(DetailAST rootAST)
        Description copied from class: AbstractCheck
        Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
        Overrides:
        beginTree in class AbstractCheck
        Parameters:
        rootAST - the root of the tree
      • leaveToken

        public void leaveToken​(DetailAST ast)
        Description copied from class: AbstractCheck
        Called after all the child nodes have been process.
        Overrides:
        leaveToken in class AbstractCheck
        Parameters:
        ast - the token leaving
      • checkNestedIdent

        private void checkNestedIdent​(DetailAST ast)
        Check if nested ident is parameter.
        Parameters:
        ast - parent of node of ident
      • visitMethodDef

        private void visitMethodDef​(DetailAST ast)
        Creates new set of parameters and store old one in stack.
        Parameters:
        ast - a method to process.
      • visitLambda

        private void visitLambda​(DetailAST lambdaAst)
        Creates new set of parameters and store old one in stack.
        Parameters:
        lambdaAst - node of type TokenTypes.LAMBDA.
      • visitMethodParameters

        private void visitMethodParameters​(DetailAST ast)
        Creates new parameter set for given method.
        Parameters:
        ast - a method for process.
      • visitLambdaParameters

        private void visitLambdaParameters​(DetailAST ast)
        Creates new parameter set for given lambda expression.
        Parameters:
        ast - a lambda expression parameter to process
      • visitParameters

        private void visitParameters​(DetailAST parametersAst)
        Visits parameter list and adds parameter names to the set.
        Parameters:
        parametersAst - ast node of type TokenTypes.PARAMETERS.