Apache Lucene 2.2.0

Apache Lucene is a high-performance, full-featured text search engine library written entirely in Java.
Apache Lucene is a technology suitable for almost any application that requires full-text search, especially cross-platform.
Main features:
- Scalable, High-Performance Indexing
- over 20MB/minute on Pentium M 1.5GHz
- small RAM requirements -- only 1MB heap
- incremental indexing as fast as batch indexing
- index size roughly 20-30% the size of text indexed
- Powerful, Accurate and Efficient Search Algorithms
- ranked searching -- best results returned first
- many powerful query types: phrase queries, wildcard queries, proximity queries, range queries and more
- fielded searching (e.g., title, author, contents)
- date-range searching
- sorting by any field
- multiple-index searching with merged results
- allows simultaneous update and searching
- Cross-Platform Solution
- Available as Open Source software under the Apache License which lets you use Lucene in both commercial and Open Source programs
- 100%-pure Java
- Implementations in other programming languages available that are index-compatible