Package com.puppycrawl.tools.checkstyle.checks

Class FinalParametersCheck

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

    Checks that parameters for methods, constructors, catch and for-each blocks are final. Interface, abstract, and native methods are not checked: the final keyword does not make sense for interface, abstract, and native method parameters as there is no code that could modify the parameter.

    Rationale: Changing the value of parameters during the execution of the method's algorithm can be confusing and should be avoided. A great way to let the Java compiler prevent this coding style is to declare parameters final.

    • Property ignorePrimitiveTypes - Ignore primitive types as parameters. Type is boolean. Default value is false.
    • Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: METHOD_DEF, CTOR_DEF.

    To configure the check to enforce final parameters for methods and constructors: 

     <module name="FinalParameters"/>

    Example: 

     public class Point {
   public Point() { } // ok
   public Point(final int m) { } // ok
   public Point(final int m,int n) { } // violation, n should be final
   public void methodOne(final int x) { } // ok
   public void methodTwo(int x) { } // violation, x should be final
   public static void main(String[] args) { } // violation, args should be final
 }

    To configure the check to enforce final parameters only for constructors: 

     <module name="FinalParameters">
   <property name="tokens" value="CTOR_DEF"/>
 </module>

    Example: 

     public class Point {
   public Point() { } // ok
   public Point(final int m) { } // ok
   public Point(final int m,int n) { } // violation, n should be final
   public void methodOne(final int x) { } // ok
   public void methodTwo(int x) { } // ok
   public static void main(String[] args) { } // ok
 }

    To configure the check to allow ignoring primitive datatypes as parameters: 

     <module name="FinalParameters">
   <property name="ignorePrimitiveTypes" value="true"/>
 </module>

    Example: 

     public class Point {
   public Point() { } // ok
   public Point(final int m) { } // ok
   public Point(final int m,int n) { } // ok
   public void methodOne(final int x) { } // ok
   public void methodTwo(int x) { } // ok
   public static void main(String[] args) { } // violation, args should be final
 }

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • final.parameter
    Since:
    3.0

    • Method Detail

      • setIgnorePrimitiveTypes

        public void setIgnorePrimitiveTypes​(boolean ignorePrimitiveTypes)
        Setter to ignore primitive types as parameters.
        Parameters:
        ignorePrimitiveTypes - true or false.

      • 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

      • visitMethod

        private void visitMethod​(DetailAST method)
        Checks parameters of the method or ctor.
        Parameters:
        method - method or ctor to check.

      • visitCatch

        private void visitCatch​(DetailAST catchClause)
        Checks parameter of the catch block.
        Parameters:
        catchClause - catch block to check.

      • visitForEachClause

        private void visitForEachClause​(DetailAST forEachClause)
        Checks parameter of the for each clause.
        Parameters:
        forEachClause - for each clause to check.

      • checkParam

        private void checkParam​(DetailAST param)
        Checks if the given parameter is final.
        Parameters:
        param - parameter to check.

      • isIgnoredParam

        private boolean isIgnoredParam​(DetailAST paramDef)
        Checks for skip current param due to ignorePrimitiveTypes option.
        Parameters:
        paramDef - PARAMETER_DEF
        Returns:
        true if param has to be skipped.