net.sourceforge.pmd.lang.java.oom.metrics

Class CycloMetric

java.lang.Object

net.sourceforge.pmd.lang.java.oom.AbstractMetric

net.sourceforge.pmd.lang.java.oom.metrics.CycloMetric

All Implemented Interfaces:

ClassMetric, Metric, OperationMetric

public final class CycloMetric
extends AbstractMetric
implements ClassMetric, OperationMetric

McCabe's Cyclomatic Complexity. Number of independent paths through a block of code [1, 2]. Formally, given that the control flow graph of the block has n vertices, e edges and p connected components, the Cyclomatic complexity of the block is given by CYCLO = e - n + 2p [2]. In practice it can be calculated by counting control flow statements following the standard rules given below.

The standard version of the metric complies with McCabe's original definition:

• +1 for every control flow statement (if, case, catch, finally, do, while, for, break, continue) and conditional expression (? : ). Notice switch cases count as one, but not the switch itself: the point is that a switch should have the same complexity value as the equivalent series of if statements.
• else and default don't count;
• +1 for every boolean operator in the guard condition of a control flow statement. That's because Java has short-circuit evaluation semantics for boolean operators, which makes every boolean operator kind of a control flow statement in itself.

Version CycloMetric.Version.IGNORE_BOOLEAN_PATHS: Boolean operators are not counted, which means that empty fall-through cases in switch statements are not counted as well.

References:

• [1] Lanza, Object-Oriented Metrics in Practice, 2005.
• [2] McCabe, A Complexity Measure, in Proceedings of the 2nd ICSE (1976).

Since:

June 2017

Author:

Clément Fournier

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CycloMetric.Version Variants of CYCLO.

Constructor Summary

Constructors

Constructor and Description
CycloMetric()

Method Summary

Methods

Modifier and Type	Method and Description
double	computeFor(ASTClassOrInterfaceDeclaration node, MetricVersion version) Actually computes the value of a metric for an AST node.
double	computeFor(ASTMethodOrConstructorDeclaration node, MetricVersion version) Actually computes the value of a metric for an AST node.

Methods inherited from class net.sourceforge.pmd.lang.java.oom.AbstractMetric

averageMetricOverOperations, findAllCalls, findOperations, getTopLevelPackageStats, highestMetricOverOperations, sumMetricOverOperations, supports

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface net.sourceforge.pmd.lang.java.oom.api.Metric

supports

Constructor Detail

CycloMetric

public CycloMetric()

Method Detail

computeFor

public double computeFor(ASTClassOrInterfaceDeclaration node,
                MetricVersion version)

Description copied from interface: ClassMetric

Actually computes the value of a metric for an AST node.

Specified by:

computeFor in interface ClassMetric

Parameters:

node - The node.

version - The version of the metric.

Returns:

The value of the metric.

computeFor

public double computeFor(ASTMethodOrConstructorDeclaration node,
                MetricVersion version)

Description copied from interface: OperationMetric

Actually computes the value of a metric for an AST node.

Specified by:

computeFor in interface OperationMetric

Parameters:

node - The node.

version - The version of the metric.

Returns:

The value of the metric.