Class `jdk.javadoc.internal.doclets.toolkit.util.IndexBuilder is used for building both the "All Classes" and the "Index" pages, the former using the class directly and the latter using subclass `HtmlIndexBuilder`. However, the separation of code between the super and subclass does not reflect these separate tasks very well. While building the "All Classes" page is much simpler than building the Index (no search index, no search tags, just one single kind of elements), a lot of the code required for the Index page is located in the base class.

The solution could be to reorganize the code so that it reflects its usage (common code in the base class, code only needed for the Index page in the subclass). Additionally, both classes should be renamed to better reflect their purpose.