private function calculateNumberOfDerivedClasses(ASTClass $class)
{
$id = $class->getId();
if (isset($this->derivedClasses[$id]) === false) {
$this->derivedClasses[$id] = 0;
}
$parentClass = $class->getParentClass();
if ($parentClass !== null && $parentClass->isUserDefined()) {
$id = $parentClass->getId();
++$this->numberOfDerivedClasses;
++$this->nodeMetrics[$id][self::M_NUMBER_OF_DERIVED_CLASSES];
}
}