| Name | Description | Type | Package | Framework |
| FST | Represents an finite state machine (FST), using a compact byte[] format. | Class | org.apache.lucene.util.fst | Apache Lucene |
| FST .Arc | Represents a single arc. | Class | org.apache.lucene.util.fst.FST | Apache Lucene |
| FST .BytesReader | Reads bytes stored in an FST. | Class | org.apache.lucene.util.fst.FST | Apache Lucene |
| FST .INPUT_TYPE | Class | org.apache.lucene.util.fst.FST | Apache Lucene | |
| FSTTester | Helper class to test FSTs. | Class | org.apache.lucene.util.fst | Apache Lucene |
| FSTTester .InputOutput | Holds one input/output pair. | Class | org.apache.lucene.util.fst.FSTTester | Apache Lucene |