Lucene - Java

Apache Lucene is a high-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform.

If you have questions about using Lucene, please post them on the Java Users mailing list.  

(The Java Developer mailing list is for discussions about developing the internals of the Lucene and Solr libraries.)