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Chapter 4. Measuring Evolving Software
General
Inner Class*
Field*
Method*
Fully Qualified Class Name
Super Class Name, Interfaces Implemented
Modifiers
Constant Pool: Numeric, String and Type Constants
Source File Name (optional)
Enclosing Class References
Annotation*
Attribute*
Name*
Modifiers, Name, Type
Annotation*
Attribute*
Modifiers, Name, Return Type, Parameter Types
Annotation*
Attribute*
Compiled Code (Java bytecode instructions)
Table 4.1: Structure of a compiled Java Class. Items that end with an
* indicate a cardinality of zero or more [180].
Java compiler and class file structure
The Java compiler reads class and interface definitions, written in the
Java programming language [108], and compiles them into class files
[131] that can be executed by the Java Virtual Machine (JVM) [180].
A compiled Java class, in contrast to natively compiled programs (for
example, a C/C++ application), retains all of the structural information
from the program code and almost all of the symbols from the
source code [184, 268]. More specifically, the compiled class contains
all information about the fields (including their types), method bodies
represented as a sequence of Java bytecode instructions, and general
information about the class (see Table 4.1 for an overview). Although,
a range of different Java compilers are available, the class files that
are generated by these compilers must adhere to the JVM specification
[180] and hence all of the data that we process to extract the metrics
matches a common specification.
The Java bytecode instructions that are generated by the compiler consists
of an opcode specifying the operation to be performed, followed
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