public void insertExistentData(){
		connectDB();
		PreparedStatement stmt = null;
		JFileChooser chooser = new JFileChooser();
		FileNameExtensionFilter filter = new FileNameExtensionFilter("txt file", "txt");
		chooser.setFileFilter(filter);
		int returnVal = chooser.showOpenDialog(chooser);
		if(returnVal == JFileChooser.APPROVE_OPTION){
//			System.out.println(chooser.getSelectedFile().getPath());
			BufferedReader br = null;
			try{
				FileReader fr = new FileReader(new File(chooser.getSelectedFile().getPath()));
				br = new BufferedReader(fr);
				String s = new String();
				String[] table_name = {"CUSTOMER","STAFF","ROOM"};
				int table_number = 0;
				while((s = br.readLine()) != null){
					if(s.length() == 0)
						continue;
					if(Character.isDigit(s.charAt(0))){
						String count = s;
						String query = "(";
						for(int i=0;i<new Integer(count).intValue();i++){
//							query = "("+br.readLine()+")";
							StringTokenizer st = new StringTokenizer(br.readLine());
							while(st.hasMoreTokens()){
								String temp = st.nextToken();
								if(Character.isDigit(temp.charAt(0))){
									query = query+new Integer(temp).intValue()+" ";
								}else{
									query = query+"\'"+temp+"\' ";
								}
							}
							query = query.substring(0, query.length()-1);
							query = query+")";
							query = query.replace(" ",",");
							query = "INSERT INTO "+table_name[table_number]+" VALUES"+query;
//							System.out.println(query);
							stmt = dbConnection.prepareStatement(query);
							stmt.executeUpdate();
							query = "(";
						}
						table_number++;
					}
				}
			}catch(Exception e){
				System.out.println(e);
			}finally{
				if(stmt != null)try{stmt.close();}catch(Exception e){};
				if(dbConnection != null)try{dbConnection.close();}catch (Exception e) {};
				if(br != null)try{ br.close();}catch (Exception e){};
			}
		}
	}