Class JavaNCSSCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class JavaNCSSCheck
    extends AbstractCheck

    Determines complexity of methods, classes and files by counting the Non Commenting Source Statements (NCSS). This check adheres to the specification for the JavaNCSS-Tool written by Chr. Clemens Lee.

    Roughly said the NCSS metric is calculated by counting the source lines which are not comments, (nearly) equivalent to counting the semicolons and opening curly braces.

    The NCSS for a class is summarized from the NCSS of all its methods, the NCSS of its nested classes and the number of member variable declarations.

    The NCSS for a file is summarized from the ncss of all its top level classes, the number of imports and the package declaration.

    Rationale: Too large methods and classes are hard to read and costly to maintain. A large NCSS number often means that a method or class has too many responsibilities and/or functionalities which should be decomposed into smaller units.

    • Property methodMaximum - Specify the maximum allowed number of non commenting lines in a method. Type is int. Default value is 50.
    • Property classMaximum - Specify the maximum allowed number of non commenting lines in a class. Type is int. Default value is 1500.
    • Property fileMaximum - Specify the maximum allowed number of non commenting lines in a file including all top level and nested classes. Type is int. Default value is 2000.
    • Property recordMaximum - Specify the maximum allowed number of non commenting lines in a record. Type is int. Default value is 150.

    To configure the check:

     <module name="JavaNCSS"/>
     

    Example:

     public void test() {
       System.out.println("Line 1");
       // another 48 lines of code
       System.out.println("Line 50") // OK
       System.out.println("Line 51") // violation, the method crosses 50 non commented lines
     }
     

    To configure the check with 40 allowed non commented lines for a method:

     <module name="JavaNCSS">
       <property name="methodMaximum" value="40"/>
     </module>
     

    Example:

     public void test() {
       System.out.println("Line 1");
       // another 38 lines of code
       System.out.println("Line 40") // OK
       System.out.println("Line 41") // violation, the method crosses 40 non commented lines
     }
     

    To configure the check to set limit of non commented lines in class to 100:

     <module name="JavaNCSS">
       <property name="classMaximum" value="100"/>
     </module>
     

    Example:

     public class Test {
       public void test() {
           System.out.println("Line 1");
           // another 47 lines of code
           System.out.println("Line 49");
       }
    
       public void test1() {
           System.out.println("Line 50"); // OK
           // another 47 lines of code
           System.out.println("Line 98"); // violation
       }
     }
     

    To configure the check to set limit of non commented lines in file to 200:

     <module name="JavaNCSS">
       <property name="fileMaximum" value="200"/>
     </module>
     

    Example:

     public class Test1 {
       public void test() {
           System.out.println("Line 1");
           // another 48 lines of code
           System.out.println("Line 49");
       }
    
       public void test1() {
           System.out.println("Line 50");
           // another 47 lines of code
           System.out.println("Line 98"); // OK
       }
     }
    
     class Test2 {
       public void test() {
           System.out.println("Line 150"); // OK
       }
    
       public void test1() {
           System.out.println("Line 200"); // violation
       }
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • ncss.class
    • ncss.file
    • ncss.method
    • ncss.record
    Since:
    3.5
    • Method Detail

      • 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
      • finishTree

        public void finishTree​(DetailAST rootAST)
        Description copied from class: AbstractCheck
        Called after finished processing a tree. Ideal place to report on information collected whilst processing a tree.
        Overrides:
        finishTree in class AbstractCheck
        Parameters:
        rootAST - the root of the tree
      • setFileMaximum

        public void setFileMaximum​(int fileMaximum)
        Setter to specify the maximum allowed number of non commenting lines in a file including all top level and nested classes.
        Parameters:
        fileMaximum - the maximum ncss
      • setClassMaximum

        public void setClassMaximum​(int classMaximum)
        Setter to specify the maximum allowed number of non commenting lines in a class.
        Parameters:
        classMaximum - the maximum ncss
      • setRecordMaximum

        public void setRecordMaximum​(int recordMaximum)
        Setter to specify the maximum allowed number of non commenting lines in a record.
        Parameters:
        recordMaximum - the maximum ncss
      • setMethodMaximum

        public void setMethodMaximum​(int methodMaximum)
        Setter to specify the maximum allowed number of non commenting lines in a method.
        Parameters:
        methodMaximum - the maximum ncss
      • isCountable

        private static boolean isCountable​(DetailAST ast)
        Checks if a token is countable for the ncss metric.
        Parameters:
        ast - the AST
        Returns:
        true if the token is countable
      • isVariableDefCountable

        private static boolean isVariableDefCountable​(DetailAST ast)
        Checks if a variable definition is countable.
        Parameters:
        ast - the AST
        Returns:
        true if the variable definition is countable, false otherwise
      • isExpressionCountable

        private static boolean isExpressionCountable​(DetailAST ast)
        Checks if an expression is countable for the ncss metric.
        Parameters:
        ast - the AST
        Returns:
        true if the expression is countable, false otherwise
      • isMethodOrCtorOrInitDefinition

        private static boolean isMethodOrCtorOrInitDefinition​(int tokenType)
        Checks if a token is a method, constructor, or compact constructor definition.
        Parameters:
        tokenType - the type of token we are checking
        Returns:
        true if token type is method or ctor definition, false otherwise