Well, there's always the option of writing some code. It is easy to create a
combination of a JTextArea and a search algorithm that relies on an entry
into a JtextField. Typically the search algorithm reacts to each entered
character by finding the first match and highlighting it. This is a nice
way to speed up the search and provide preliminary general results as the
user types in a specific query.

BTW this is exactly how the Mozilla search feature works.