Lucene 2.9.4 demo API

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




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");
    IndexWriter iwriter = new IndexWriter(directory, analyzer, true,
                                          new IndexWriter.MaxFieldLength(25000));
    Document doc = new Document();
    String text = "This is the text to be indexed.";
    doc.add(new Field("fieldname", text, Field.Store.YES,
    // Now search the index:
    IndexSearcher isearcher = new IndexSearcher(directory, true)// read-only=true
    // Parse a simple query that searches for "text":
    QueryParser parser = new QueryParser("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.jar:lucene-demo.jar org.apache.lucene.demo.IndexFiles
  [ ... ]

> java -cp lucene.jar:lucene-demo.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. ]

The IndexHTML demo is more sophisticated.  It incrementally maintains an index of HTML files, adding new files as they appear, deleting old files as they disappear and re-indexing files as they change.
> java -cp lucene.jar:lucene-demo.jar org.apache.lucene.demo.IndexHTML -create java/jdk1.1.6/docs/relnotes
adding java/jdk1.1.6/docs/relnotes/SMICopyright.html
  [ ... create an index containing all the relnotes ]

> rm java/jdk1.1.6/docs/relnotes/smicopyright.html

> java -cp lucene.jar:lucene-demo.jar org.apache.lucene.demo.IndexHTML java/jdk1.1.6/docs/relnotes
deleting java/jdk1.1.6/docs/relnotes/SMICopyright.html

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