Lucene 9.1.0 core API

Apache Lucene is a high-performance, full-featured text search engine library. Here's a simple example how to use Lucene for indexing and searching (using JUnit to check if the results are what we expect):

    Analyzer analyzer = new StandardAnalyzer();

    Path indexPath = Files.createTempDirectory("tempIndex");
    Directory directory =;
    IndexWriterConfig config = new IndexWriterConfig(analyzer);
    IndexWriter iwriter = new IndexWriter(directory, config);
    Document doc = new Document();
    String text = "This is the text to be indexed.";
    doc.add(new Field("fieldname", text, TextField.TYPE_STORED));
    // Now search the index:
    DirectoryReader ireader =;
    IndexSearcher isearcher = new IndexSearcher(ireader);
    // Parse a simple query that searches for "text":
    QueryParser parser = new QueryParser("fieldname", analyzer);
    Query query = parser.parse("text");
    ScoreDoc[] hits =, 10).scoreDocs;
    assertEquals(1, hits.length);
    // Iterate through the results:
    for (int i = 0; i < hits.length; i++) {
      Document hitDoc = isearcher.doc(hits[i].doc);
      assertEquals("This is the text to be indexed.", hitDoc.get("fieldname"));

The Lucene API is divided into several packages:

To use Lucene, an application should:
  1. Create Documents by adding Fields;
  2. Create an IndexWriter and add documents to it with addDocument();
  3. Call QueryParser.parse() to build a query from a string; and
  4. Create an IndexSearcher and pass the query to its search() method.
Some simple examples of code which does this are: To demonstrate these, try something like:
> java -cp lucene-core.jar:lucene-demo.jar:lucene-analysis-common.jar org.apache.lucene.demo.IndexFiles -index index -docs
  [ ... ]

> java -cp lucene-core.jar:lucene-demo.jar:lucene-queryparser.jar:lucene-analysis-common.jar org.apache.lucene.demo.SearchFiles
Query: chowder
Searching for: chowder
34 total matching documents
  [ ... thirty-four documents contain the word "chowder" ... ]

Query: "clam chowder" AND Manhattan
Searching for: +"clam chowder" +manhattan
2 total matching documents
  [ ... two documents contain the phrase "clam chowder" and the word "manhattan" ... ]
    [ Note: "+" and "-" are canonical, but "AND", "OR" and "NOT" may be used. ]

Text analysis.
Fast, general-purpose grammar-based tokenizer StandardTokenizer implements the Word Break rules from the Unicode Text Segmentation algorithm, as specified in Unicode Standard Annex #29.
General-purpose attributes for text analysis.
Codecs API: API for customization of the encoding and structure of the index.
Compressing helper classes.
Lucene 9.0 file format.
BlockTree terms dictionary.
Lucene 9.0 compressing format.
Lucene 9.1 file format.
Postings format that can delegate to different formats per-field.
The logical representation of a Document for indexing and searching.
Geospatial Utility Implementations for Lucene Core
Code to maintain and access indices.
Internal bridges to package-private internals, for use by the lucene test framework only.
Code to search indices.
Comparators, used to compare hits so as to determine their sort order when collecting the top results with TopFieldCollector.
This package contains the various ranking models that can be used in Lucene.
Binary i/o API, used for all index data.
Some utility classes.
Finite-state automaton for regular expressions.
Block KD-tree, implementing the generic spatial data structure described in this paper.
Compression utilities.
Finite state transducers
Utility classes for working with token streams as graphs.
Navigable Small-World graph, nominally Hierarchical but currently only has a single layer.
package holding hppc related classes.
Comparable object wrappers
Packed integer arrays and streams.