Laurie Williams, Dright Ho, and Sarah Heckman. [Contact Authors]
CSC 326 - Software Engineering
Department of Computer Science
North Carolina State University

Back to Software Engineering Tutorials

To view metrics on a project, first open up the Metrics view by selecting Window > Show View > Other.... Open up the Metrics tab and select Metrics.

In order to display metrics about a project you must enable the project to calculate metrics. Make sure you are in the Java Perspective and have your project open in the Package Explorer. Right click on a project and select Properties. Select Metrics on the left side, and check the Enable Metrics checkbox. Rebuild the project by selecting Project > Build Project (make sure you have the project that you want to build selected in Package Explorer.) If you have Build Automatically enabled, you will not be able to build your project in this manner. Just change a file and save. The project will be rebuilt for you, and the metrics will be calculated. The metrics will be displayed in the Metrics view.

There are 23 metrics that are displayed in the metrics view, and they are discussed in section 4 . If the metric is out of optimal range, then the metric is highlighted in red. Otherwise the metric is highlighted in blue if they are in range, and black if the metric cannot be calculated. Each metric has a plus box beside it that expands so that you can study the metrics on all source folders, packages and, where applicable, on class files and methods. Below are some of the metrics for the Coffee Maker example.

Metrics for the CoffeeMaker Example

The metrics information given below was obtained directly from the Metrics plugin website: http://metrics.sourceforge.net/. The author of the metrics plug-in used "Object-Oriented Metrics, measures of Complexity" by Brian Henderson-Sellers and "OO Design Quality Metrics, An Analysis of Dependencies" by Robert C. Martin to obtain the definitions of the metrics used for this plug-in.

• Lines of Code (LOC): Total lines of code in the selected scope. Only counts non-blank and non-comment lines inside method bodies.
• Number of Static Methods (NSM): Total number of static methods in the selected scope.
• Afferent Coupling (CA):The number of classes outside a package that depend on classes inside the package.
• Normalized Distance (RMD): | RMA + RMI - 1 |, this number should be small, close to zero for good packaging design.
• Number of Classes (NOC): Total number of classes in the selected scope
• Specialization Index (SIX): Average of the specialization index, defined as NORM * DIT / NOM. This is a class level metric
• Instability (RMI): CE / (CA + CE)
• Number of Attributes (NOF): Total number of attributes in the selected scope.
• Number of Packages (NOP): Total number of packages in the selected scope.
• Method Lines of Code (MLOC): Total number of lines of code inside method bodies, excluding blank lines and comments.
• Weighted Methods per Class (WMC): Sum of the McCabe Cyclomatic Complexity for all methods in a class.
• Number of Overridden Methods (NORM):Total number of methods in the selected scope that are overridden from an ancestor class.
• Number of Static Attributes (NSF): Total number of static attributes in the selected scope.
• Nested Block Depth (NBD): The depth of nested blocks of code.
• Number of Methods (NOM): Total number of methods defined in the selected scope.
• Lack of Cohesion of Methods (LCOM): A measure for the Cohesiveness of a class. Calculated with the Henderson-Sellers method: If m(A) is the number of methods accessing an attribute A, calculate the average of m(A) for all attributes, subtract the number of methods m and divide the result by (1-m). A low value indicates a cohesive class and a value close to 1 indicates a lack of cohesion and suggests the class might better be split into a number of (sub)classes.
• McCabe Cyclomatic Complexity (VG): Counts the number of flows through a piece of code. Each time a branch occurs (if, for, while, do, case, catch and the ?: ternary operator, as well as the && and || conditional logic operators in expressions) this metric is incremented by one. Calculated for methods only. For a full treatment of this metric see McCabe.
• Number of Parameters (PAR): Total number of parameters in the selected scope.
• Abstractness (RMA): The number of abstract classes (and interfaces) divided by the total number of types in a package.
• Number of Interfaces (NOI): Total number of interfaces in the selected scope.
• Efferent Coupling (CE): The number of classes inside a package that depend on classes outside the package.
• Number of Children (NSC): Total number of direct subclasses of a class.
• Depth of Inheritance Tree (DIT): Distance from class Object in inheritance hierarchy.

The safe range for each metric can be changed in the Window > Preferences menu. However, some safe ranges of metrics are provided for you.

• Lines of Code (Method Level): Max 50 - If a method is over 50 lines of code it is suggested that the method be broken up for readability and maintainability.
• Nested Block Depth (Method Level): Max 5 - If a block of code has over 5 nested loops, break up the method.
• Lines of Code (Class Level): Max 750 - If a class has over 750 lines of code split up the class and delegate it's responsibilities.
• McCabe Cyclomatic Complexity (Method Level): Max 10 - If a method has over 10 different loops, break up the method.
• Number of Parameters (Method Level): Max 5 - A method should have no more than 5 parameters. If it does create an object and pass the object to the method.