Apache Lucene Core is an open source library for full-featured text search engines written in Java. It uses tokenization for breaking text into small chunks for indexing elements. It also provide pre- and post-tokenization options for analysis purposes. It supports stemming, filtering, text-normalization, and synonym-expansion after tokenization. When used, it creates a directory and index files, and can be used to search the contents. It cannot be taken as an NLP toolkit, but it provides powerful tools for working with text and advanced string-manipulation with tokenization. It provides a free search engine. The following table list the important links for Apache Lucene: