public HashMap<String, Double> searchSingleWord(String search_word) throws Exception
		{
				HashMap<String, Double> doc_weight_map = new HashMap<String, Double>();

				Path src_doc_path = new Path(src_path);
				FileStatus[] src_doc_list = fs.listStatus(src_doc_path);
				final int doc_num = src_doc_list.length;

				Path index_file_path = new Path(index_file_name);
				FSDataInputStream in = fs.open(index_file_path);
				BufferedReader br_in = new BufferedReader(new InputStreamReader(in));
				String message_in;
			    while( (message_in = br_in.readLine()) != null)
				{
					String[] word_and_info = message_in.split("\t");
					String word = word_and_info[0];

					if(ignore_case_flag == true)
					{
							word = word.toLowerCase();
							search_word = search_word.toLowerCase();
					}

					if(word.equals(search_word))
					{
						String[] word_info = word_and_info[1].split(" ");
						int doc_freq = Integer.parseInt(word_info[1].trim());
						String[] doc_and_info = word_info[2].split("\\]");

						for( int i=0; i<doc_freq; i++ )
						{
								String[] doc_and_info_token = doc_and_info[i].split("\\[");
								String file_name = doc_and_info_token[0];
								String[] info_token = doc_and_info_token[1].split(":");
								int term_freq = Integer.parseInt(info_token[0]);
								double tf_idf = term_freq * Math.log10(1.0 * doc_num / doc_freq);

								/*
								System.out.println(term_freq);
								System.out.println(doc_num);
								System.out.println(doc_freq);
								*/

								doc_weight_map.put(file_name, new Double(tf_idf));
						}
					}
				}
				in.close();
				return doc_weight_map;
		}