Package com.puppycrawl.tools.checkstyle.checks.metrics

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

    • Field Detail

      • MSG_METHOD

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

      • MSG_CLASS

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

      • MSG_RECORD

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

      • MSG_FILE

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

    • Constructor Detail

      • JavaNCSSCheck

        public JavaNCSSCheck()

    • 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

      • 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