- To ensure accurate test runs on Java applications, developers need to know how much of
- the code has been tested, and where to find any untested code. Coverage helps you
- locate untested code, and measure precisely how much code has been exercised.
- The result is a higher quality application in a shorter period of time.
-
-
The perpendicular distance of a package from the idealized line A + I = 1. This metric is an indicator of the package's balance between abstractness and stability.
-
A package squarely on the main sequence is optimally balanced with respect to its abstractness and stability. Ideal packages are either completely abstract and stable (x=0, y=1) or completely concrete and instable (x=1, y=0).
-
The range for this metric is 0 to 1, with D=0 indicating a package that is coincident with the main sequence and D=1 indicating a package that is as far from the main sequence as possible.
The perpendicular distance of a package from the idealized line A + I = 1. This metric is an indicator of the package's balance between abstractness and stability.
-
A package squarely on the main sequence is optimally balanced with respect to its abstractness and stability. Ideal packages are either completely abstract and stable (x=0, y=1) or completely concrete and instable (x=1, y=0).
-
The range for this metric is 0 to 1, with D=0 indicating a package that is coincident with the main sequence and D=1 indicating a package that is as far from the main sequence as possible.
- Note: Rules checked have originated from style guidelines suggested by the language designers,
- experience from the Java development community and insite experience. Violations are generally
- reported with a reference to the Java Language Specifications (JLS x.x.x)
- and Metamata Audit rules (x.x).
- Please consult these documents for additional information about violations.
-
- Rules checked also enforce adherence to Sun Java coding guidelines in use at Jakarta.
-
- One should note that these violations do not necessary underline errors but should be used
- as an indication for possible errors. As always, use your best judgment and review
- them carefully, it might save you hours of debugging.
-
-This metric was introduced in the 1970s to measure the amount of control
-flow complexity or branching complexity in a module such as a
-subroutine. It gives the number of paths that may be taken through the
-code, and was initially developed to give some measure of the cost of
-producing a test case for the module by executing each path.
-
-Methods with a high cyclomatic complexity tend to be more difficult to
-understand and maintain. In general the more complex the methods of an
-application, the more difficult it will be to test it, and this will adversely
-affect its reliability.
-
-V(G) is a measure of the control flow complexity of a method or
-constructor. It counts the number of branches in the body of the method,
-defined as:
-
-
while statements;
-
if statements;
-
for statements.
-
-
-The metric can also be configured to count each case of a switch
-statement as well.
-
-
-
Lines of Code - LOC
-
-This is perhaps the simplest of all the metrics to define and compute.
-Counting lines has a long history as a software metric dating from before
-the rise of structured programming, and it is still in widespread use today.
-The size of a method affects the ease with which it can be understood, its
-reusability and its maintainability. There are a variety of ways that the size
-can be calculated. These include counting all the lines of code, the number
-of statements, the blank lines of code, the lines of commentary, and the
-lines consisting only of syntax such as block delimiters.
-
-This metric can also be used for sizing other constructs as well, for
-example, the overall size of a Java class or package can be measured by
-counting the number of source lines it consists of.
-
-LOC can be used to determine the size of a compilation unit (source file),
-class or interface, method, constructor, or field. It can be configured to
-ignore:
-
-
blank lines;
-
lines consisting only of comments;
-
lines consisting only of opening and closing braces.
-
-
-
-
Depth of Inheritance Hierarchy - DIT
-
-This metric calculates how far down the inheritance hierarchy a class is
-declared. In Java all classes have java.lang.Object as their ultimate
-superclass, which is defined to have a depth of 1. So a class that
-immediately extends java.lang.Object has a metric value of 2; any of its
-subclasses will have a value of 3, and so on.
-
-A class that is deep within the tree inherits more methods and state
-variables, thereby increasing its complexity and making it difficult to
-predict its behavior. It can be harder to understand a system with many
-inheritance layers.
-
-DIT is defined for classes and interfaces:
-
-
all interface types have a depth of 1;
-
the class java.lang.Object has a depth of 1;
-
all other classes have a depth of 1 + the depth of their super class.
-
-
-
-
Number of Attributes - NOA
-
-The number of distinct state variables in a class serves as one measure of
-its complexity. The more state a class represents the more difficult it is to
-maintain invariants for it. It also hinders comprehensibility and reuse.
-
-In Java, state can be exposed to subclasses through protected fields, which
-entails that the subclass also be aware of and maintain any invariants. This
-interference with the class's data encapsulation can be a source of defects
-and hidden dependencies between the state variables.
-
-NOA is defined for classes and interfaces. It counts the number of fields
-declared in the class or interface.
-
-
-
Number of Remote Methods - NRM
-
-NRM is defined for classes. A remote method call is defined as an
-invocation of a method that is not declared in any of:
-
-
the class itself;
-
a class or interface that the class extends or implements;
-
a class or method that extends the class.
-
-
-The value is the count of all the remote method calls in all of the methods
-and constructors of the class.
-
-
-
Number of Local Methods - NLM
-
-NLM is defined for classes and interfaces. A local method is defined as a
-method that is declared in the class or interface. NLM can be configured to
-include the local methods of all of the class's superclasses. Methods with
-public, protected, package and private visibility can be independently
-counted by setting configuration parameters.
-
-
-
Weighted Methods per Class - WMC
-
-If the number of methods in a class can be determined during the design
-and modeling phase of a project, it can be used as a predictor of how
-much time and effort is needed to develop, debug and maintain it. This
-metric can be further refined by incorporating a weighting for the
-complexity of each method. The usual weighting is given by the cyclomatic
-complexity of the method.
-
-The subclasses of a class inherit all of its public and protected methods,
-and possibly its package methods as well, so the number of methods a
-class has directly impacts the complexity of its subclasses. Classes with
-large numbers of methods are often specific to a particular application,
-reducing the ability to reuse them.
-
-The definition of WMC is based upon NLM, and it provides the same
-configuration parameters for counting inherited methods and of varying
-visibility. The main difference is that NLM always counts each method as 1,
-whereas WMC will weight each method. There are two weighting schemes:
-
-
V(G) the cyclomatic complexity of the method is used as its weight.
- Methods from class files are given a V(G) of 1.
-
the arity, or the number of parameters of the method are used to
- determine the weight.
-
-
-
-
Response For Class - RFC
-
-The response set of a class is the set of all methods that can be invoked as
-a result of a message sent to an object of the class. This includes methods
-in the class's inheritance hierarchy and methods that can be invoked on
-other objects. The Response For Class metric is defined to be size of the
-response set for the class. A class which provides a larger response set is
-considered to be more complex than one with a smaller response set.
-
-One reason for this is that if a method call on a class can result in a large
-number of different method calls on the target and other classes, then it
-can be harder to test the behavior of the class and debug problems. It will
-typically require a deeper understanding of the potential interactions that
-objects of the class can have with the rest of the system.
-
-RFC is defined as the sum of NLM and NRM for the class. The local methods
-include all of the public, protected, package and private methods, but not
-methods declared only in a superclass.
-
-
-
Data Abstraction Coupling - DAC
-
-DAC is defined for classes and interfaces. It counts the number of reference
-types that are used in the field declarations of the class or interface. The
-component types of arrays are also counted. Any field with a type that is
-either a supertype or a subtype of the class is not counted.
-
-
-
Fan Out - FANOUT
-
-FANOUT is defined for classes and interfaces, constructors and methods. It
-counts the number of reference types that are used in:
-
-
field declarations;
-
formal parameters and return types;
-
throws declarations;
-
local variables.
-
-
-The component types of arrays are also counted. Any type that is either a
-supertype or a subtype of the class is not counted.
-
-
-
Coupling Between Objects - CBO
-
-When one object or class uses another object or class they are said to be
-coupled. One major source of coupling is that between a superclass and a
-subclass. A coupling is also introduced when a method or field in another
-class is accessed, or when an object of another class is passed into or out
-of a method invocation. Coupling Between Objects is a measure of the
-non-inheritance coupling between two objects.
-
-A high value of coupling reduces the modularity of the class and makes
-reuse more difficult. The more independent a class is the more likely it is
-that it will be possible to reuse it in another part of the system. When a
-class is coupled to another class it becomes sensitive to changes in that
-class, thereby making maintenance for difficult. In addition, a class that is
-overly dependent on other classes can be difficult to understand and test in
-isolation.
-
-CBO is defined for classes and interfaces, constructors and methods. It
-counts the number of reference types that are used in:
-
-
field declarations
-
formal parameters and return types
-
throws declarations
-
local variables
-
-
-It also counts:
-
-
types from which field and method selections are made
-
-
-The component types of arrays are also counted. Any type that is either a
-supertype or a subtype of the class is not counted.
-
-
-
Lack of Cohesion Of Methods - LCOM
-
-The cohesion of a class is the degree to which its methods are related to
-each other. It is determined by examining the pattern of state variable
-accesses within the set of methods. If all the methods access the same state
-variables then they have high cohesion; if they access disjoint sets of
-variables then the cohesion is low. An extreme example of low cohesion
-would be if none of the methods accessed any of the state variables.
-
-If a class exhibits low method cohesion it indicates that the design of the
-class has probably been partitioned incorrectly, and could benefit by being
-split into more classes with individually higher cohesion. On the other
-hand, a high value of cohesion (a low lack of cohesion) implies that the
-class is well designed. A cohesive class will tend to provide a high degree
-of encapsulation, whereas a lack of cohesion decreases encapsulation and
-increases complexity.
-
-Another form of cohesion that is useful for Java programs is cohesion
-between nested and enclosing classes. A nested class that has very low
-cohesion with its enclosing class would probably better designed as a peer
-class rather than a nested class.
-
-LCOM is defined for classes. Operationally, LCOM takes each pair of
-methods in the class and determines the set of fields they each access. If
-they have disjoint sets of field accesses increase the count P by one. If they
-share at least one field access then increase Q by one. After considering
-each pair of methods,
-LCOM = (P > Q) ? (P - Q) : 0
-
-Indirect access to fields via local methods can be considered by setting a
-metric configuration parameter.
-
-
-
Number Of Classes - NOC
-
-The overall size of the system can be estimated by calculating the number
-of classes it contains. A large system with more classes is more complex
-than a smaller one because the number of potential interactions between
-objects is higher. This reduces the comprehensibility of the system which
-in turn makes it harder to test, debug and maintain.
-
-If the number of classes in the system can be projected during the initial
-design phase of the project it can serve as a base for estimating the total
-effort and cost of developing, debugging and maintaining the system.
-
-The NOC metric can also usefully be applied at the package and class level
-as well as the total system.
-
-NOCL is defined for class and interfaces. It counts the number of classes or
-interfaces that are declared. This is usually 1, but nested class declarations
-will increase this number.
-
-
-
-
-
-
- .bannercell {
- border: 0px;
- padding: 0px;
- }
- body {
- margin-left: 10;
- margin-right: 10;
- font:normal 80% arial,helvetica,sanserif;
- background-color:#FFFFFF;
- color:#000000;
- }
- .a td {
- background: #efefef;
- }
- .b td {
- background: #fff;
- }
- th, td {
- text-align: left;
- vertical-align: top;
- }
- th {
- font-weight:bold;
- background: #ccc;
- color: black;
- }
- table, th, td {
- font-size:100%;
- border: none
- }
- table.log tr td, tr th {
-
- }
- h2 {
- font-weight:bold;
- font-size:140%;
- margin-bottom: 5;
- }
- h3 {
- font-size:100%;
- font-weight:bold;
- background: #525D76;
- color: white;
- text-decoration: none;
- padding: 5px;
- margin-right: 2px;
- margin-left: 2px;
- margin-bottom: 0;
- }
- .Error {
- font-weight:bold; color:red;
- }
-
-
-
-
-
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-
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-
-
-
-
-
-
-
- Note: Metrics evaluate the quality of software by analyzing the program source and quantifying
- various kind of complexity. Complexity is a common source of problems and defects in software.
- High complexity makes it more difficult to develop, understand, maintain, extend, test and debug
- a program.
-
- The primary use of metrics is to focus your attention on those parts of code that potentially are
- complexity hot spots. Once the complex areas your program have been uncovered, you can take remedial
- actions.
- For additional information about metrics and their meaning, please consult
- Metamata Metrics manual.
-
-
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-
-
Packages
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Package
-
-
-
-
-
-
-
-
-
- Note: Metrics evaluate the quality of software by analyzing the program source and quantifying
- various kind of complexity. Complexity is a common source of problems and defects in software.
- High complexity makes it more difficult to develop, understand, maintain, extend, test and debug
- a program.
-
- The primary use of metrics is to focus your attention on those parts of code that potentially are
- complexity hot spots. Once the complex areas your program have been uncovered, you can take remedial
- actions.
- For additional information about metrics and their meaning, please consult
- Metamata Metrics manual.
-
-
-