Lucene 4.5.0 core API

Apache Lucene is a high-performance, full-featured text search engine library.


org.apache.lucene Top-level package.
org.apache.lucene.analysis API and code to convert text into indexable/searchable tokens.
org.apache.lucene.analysis.tokenattributes General-purpose attributes for text analysis.
org.apache.lucene.codecs Codecs API: API for customization of the encoding and structure of the index.
org.apache.lucene.codecs.compressing StoredFieldsFormat that allows cross-document and cross-field compression of stored fields.
org.apache.lucene.codecs.lucene3x Codec to support Lucene 3.x indexes (readonly)
org.apache.lucene.codecs.lucene40 Lucene 4.0 file format.
org.apache.lucene.codecs.lucene41 Lucene 4.1 file format.
org.apache.lucene.codecs.lucene42 Lucene 4.2 file format.
org.apache.lucene.codecs.lucene45 Lucene 4.5 file format.
org.apache.lucene.codecs.perfield Postings format that can delegate to different formats per-field.
org.apache.lucene.document The logical representation of a Document for indexing and searching.
org.apache.lucene.index Code to maintain and access indices. Code to search indices. The payloads package provides Query mechanisms for finding and using payloads. This package contains the various ranking models that can be used in Lucene. The calculus of spans. Binary i/o API, used for all index data.
org.apache.lucene.util Some utility classes.
org.apache.lucene.util.automaton Finite-state automaton for regular expressions.
org.apache.lucene.util.fst Finite state transducers
org.apache.lucene.util.mutable Comparable object wrappers
org.apache.lucene.util.packed Packed integer arrays and streams.


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(Version.LUCENE_CURRENT);

    // Store the index in memory:
    Directory directory = new RAMDirectory();
    // To store an index on disk, use this instead:
    //Directory directory ="/tmp/testindex");
    IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_CURRENT, 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(Version.LUCENE_CURRENT, "fieldname", analyzer);
    Query query = parser.parse("text");
    ScoreDoc[] hits =, null, 1000).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-analyzers-common.jar org.apache.lucene.demo.IndexFiles -index index -docs
  [ ... ]

> java -cp lucene-core.jar:lucene-demo.jar:lucene-queryparser.jar:lucene-analyzers-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. ]

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