public  void createAndInsertInverseIndex() {

		MongoCollection<Document> collection = database.getCollection(indexName);
		MongoCollection<Document> inverseIndexcollection = database.getCollection(inverseIndexName);
		try (MongoCursor<Document> cur = collection.find().iterator()) {
			while (cur.hasNext()) {
				Document doc = cur.next();

				String docName = doc.getString("docID");
				List<Document> idxEntries = (List<Document>) doc.get("wordsList");

				BasicDBObject basic = new BasicDBObject();
				BasicDBObject basic1 = new BasicDBObject();
				BasicDBObject basic2 = new BasicDBObject();
				List<String> docsList;
				//System.out.println(docName);

				for(int i=0;i<idxEntries.size();i++)
				{

					basic1.append("wordID",idxEntries.get(i).getString("word"));

					//	MongoCursor<Document> cursor = inverseIndexcollection.find(basic1).first();

					if ( inverseIndexcollection.find(basic1).first()== null)
					{

						//System.out.println("insert ");
						docsList = new ArrayList<String>();
						docsList.add(docName);
						Document document = new Document( basic1.append("docsList", docsList));
						inverseIndexcollection.insertOne(document);

						docsList.clear();
						document.clear();

					}
					else
					{
						//System.out.println("update ");
						basic.append("docsList", docName);
						basic2.append("$addToSet", basic);
						inverseIndexcollection.updateOne(basic1,basic2);
						basic.clear();basic2.clear();
					}
					basic1.clear();
				}


			}
		}
	}