thesis - Faculty of Information and Communication Technologies ...

Chapter 4. Measuring Evolving Software
Abbv. Name Description
IAS Is Abstract A flag that is set to 1, if class is abstract
IEX Is Exception A flag that is set to 1 if class has
java.lang.Throwable as an ancestor
INF Is Interface A flag that is set to 1 if class is an interface
IPI Is Private A flag that is set to 1 if class is private
IPR Is Protected A flag that is set to 1 if class is protected
IPU Is Public A flag that is set to 1 if class is public
IPK Is Package
Accessible
A flag that is set to 1 if the class has no
visibility modifier and hence would revert to
having package visibility
Table 4.4: Flags extracted for each class.
Once information from all the classes is extracted, we remove classes
that are from external libraries that are not part of the core software
system under study. Though, we ensure that the set of input JAR files
used in the Jar Extraction step does not consist of any external libraries
(see Section 4.5.1), this additional step was needed since some projects
merged all external library code into their core JAR file in order to reduce
the number of different files that needed to be distributed. We
identify and removed the set of classes that are from external libraries
using the same process that we applied during the Jar Extraction step
(see Section 4.5.1).
The Java programming language provides developers the option for creating
two different types of abstractions: a class, and an interface [108].
Within the context of our study, the key distinction between these two
abstractions is that interfaces do not contain any method bodies and
hence the metrics defined in Table 4.3 are not available for compiled
Java interfaces which do not contain bytecode instructions in the method
section of a class file. However, all of the other information (see Table
4.1) is available and therefore used to compute the metrics defined
in Table 4.2 and Table 4.4. We are also able to extract dependency information
from an interface, that is, other Java classes that an interface
depends upon (discussed in Section 4.5.4). In the rest of this thesis, to
improve readability, we use the term class to indicate a compiled Java
class, and it may be either a Java interface or a Java class. We use
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