MG4J: Managing Gigabytes for Java

MG4J: Managing Gigabytes for Java™: "MG4J (Managing Gigabytes for Java) is a free full-text indexing system for large document collections written in Java. As a by-product, it offers several general-purpose optimised classes, including fast & compact mutable strings, bit-level I/O, fast unsychronised buffered streams, (possibly signed) minimal perfect hashing for very large strings collections, etc."

For those that don't know, "Managing Gigabytes" is a great book.