The module ClassList is for separating namespaces. It contains the logic to create a list of all classes of all JDK versions. The main logic is performed in ClassList::JarSearcher, which creates the ClassList::List. It uses a Classpath::CompositeClasspath to find all classes and ClassFile::JavaClassHeader to read the class information from. The generated list contains packages and these packages contain the names of classes, their accessibility and the versions they were added (or removed) from JDK. ClassList is an "application" using the JavaClass infrastructure. For a full example see how to generate lists of JDK classes.