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 Details

    • MSG_KEY

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

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

      private Set<String> parameterNames
      Current set of parameters.
  • Constructor Details

    • ParameterAssignmentCheck

      public ParameterAssignmentCheck()
  • 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:
    • 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:
    • 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:
    • 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
    • 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
    • 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.