#vulnerable code 
                                @Override
    public int read(String table, String key, Set<String> fields,
            HashMap<String, ByteIterator> result) {
        try {
            MongoCollection<Document> collection = database
                    .getCollection(table);
            Document query = new Document("_id", key);

            FindIterable<Document> findIterable = collection
                                                  .withReadPreference(readPreference)
                                                  .find(query);

            Document queryResult = null;
            if (fields != null) {
                Document projection = new Document();
                for (String field : fields) {
                    projection.put(field, INCLUDE);
                }
                findIterable.projection(projection);
            }

            queryResult = findIterable.first();

            if (queryResult != null) {
                fillMap(result, queryResult);
            }
            return queryResult != null ? 0 : 1;
        }
        catch (Exception e) {
            System.err.println(e.toString());
            return 1;
        }
    } 
                            #location 10 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    public int read(String table, String key, Set<String> fields,
            HashMap<String, ByteIterator> result) {
        try {
            MongoCollection<Document> collection = database
                    .getCollection(table);
            Document query = new Document("_id", key);

            FindIterable<Document> findIterable = collection.find(query);

            Document queryResult = null;
            if (fields != null) {
                Document projection = new Document();
                for (String field : fields) {
                    projection.put(field, INCLUDE);
                }
                findIterable.projection(projection);
            }

            queryResult = findIterable.first();

            if (queryResult != null) {
                fillMap(result, queryResult);
            }
            return queryResult != null ? 0 : 1;
        }
        catch (Exception e) {
            System.err.println(e.toString());
            return 1;
        }
    }