No class definition found error occurs while trying to run the lucene app from command line

Question

I'm a beginner to lucene and I had tried to run a sample app (HelloLucene.java) given in the website http://www.lucenetutorial.com/lucene-in-5-minutes.html. The code was successfully compiled and a class file (HelloLucene.class) was created for the app.

But while trying to run the app, following error occurs

• could not find or load main class HelloLucene

I had referred with the link Java program uses or overrides a deprecated API? and tried the solutions provided, but all in vain. please help me to solve this problem.

The command which I used to run the code is

• java HelloLucene lucene

code which I tried to run:

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.queryParser.ParseException;
import org.apache.lucene.queryParser.QueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopScoreDocCollector;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.util.Version;

import java.io.IOException;

public class HelloLucene {
  public static void main(String[] args) throws IOException, ParseException {
// 0. Specify the analyzer for tokenizing text.
//    The same analyzer should be used for indexing and searching
StandardAnalyzer analyzer = new StandardAnalyzer(Version.LUCENE_35);

// 1. create the index
Directory index = new RAMDirectory();

IndexWriterConfig config = new IndexWriterConfig(Version.LUCENE_35, analyzer);

IndexWriter w = new IndexWriter(index, config);
addDoc(w, "Lucene in Action");
addDoc(w, "Lucene for Dummies");
addDoc(w, "Managing Gigabytes");
addDoc(w, "The Art of Computer Science");
w.close();

// 2. query
String querystr = args.length > 0 ? args[0] : "lucene";

// the "title" arg specifies the default field to use
// when no field is explicitly specified in the query.
Query q = new QueryParser(Version.LUCENE_35, "title", analyzer).parse(querystr);

// 3. search
int hitsPerPage = 10;
IndexReader reader = IndexReader.open(index);
IndexSearcher searcher = new IndexSearcher(reader);
TopScoreDocCollector collector = TopScoreDocCollector.create(hitsPerPage, true);
searcher.search(q, collector);
ScoreDoc[] hits = collector.topDocs().scoreDocs;

// 4. display results
System.out.println("Found " + hits.length + " hits.");
for(int i=0;i<hits.length;++i) {
  int docId = hits[i].doc;
  Document d = searcher.doc(docId);
  System.out.println((i + 1) + ". " + d.get("title"));
}

// searcher can only be closed when there
// is no need to access the documents any more. 
searcher.close();
}

 private static void addDoc(IndexWriter w, String value) throws IOException {
   Document doc = new Document();
   doc.add(new Field("title", value, Field.Store.YES, Field.Index.ANALYZED));
   w.addDocument(doc);
 }
}

Answer 1

Looks like you need to set the classpath, to include both the Lucene JAR file and the directory that contains the HelloLucene class. The whole command should look like this:

java -classpath .:lucene-core-3.4.0.jar HelloLucene lucene