JavaNCSS

Since Checkstyle 3.5

Description

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.

Properties

name description type default value since
classMaximum Specify the maximum allowed number of non commenting lines in a class. int 1500 3.5
fileMaximum Specify the maximum allowed number of non commenting lines in a file including all top level and nested classes. int 2000 3.5
methodMaximum Specify the maximum allowed number of non commenting lines in a method. int 50 3.5
recordMaximum Specify the maximum allowed number of non commenting lines in a record. int 150 8.36

Examples

To configure the check: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="JavaNCSS"/>
  </module>
</module>

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="Checker">
  <module name="TreeWalker">
    <module name="JavaNCSS">
      <property name="methodMaximum" value="40"/>
    </module>
  </module>
</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="Checker">
  <module name="TreeWalker">
    <module name="JavaNCSS">
      <property name="classMaximum" value="100"/>
    </module>
  </module>
</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="Checker">
  <module name="TreeWalker">
    <module name="JavaNCSS">
      <property name="fileMaximum" value="200"/>
    </module>
  </module>
</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
  }
}

Example of Usage

Violation Messages

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Package

com.puppycrawl.tools.checkstyle.checks.metrics

Parent Module

TreeWalker