public static ForwardIndex getForwardIndex(int docId, String word) {
		ForwardIndex forwardIndex = null;
		
		try{
			conn = DBConnection.getConnectionInstance();
			String sql = "select * from forward_index where docId = ? and word = ?";
			
			PreparedStatement preparedStatement = conn.prepareStatement(sql);
			preparedStatement.setInt(1, docId);
			preparedStatement.setString(2, word);
			
			int cnt = 0;
			ResultSet rs = preparedStatement.executeQuery();
			forwardIndex = new ForwardIndex();
			while(rs.next()) {
				++cnt;
				
				forwardIndex.setForwardId(rs.getInt(1));
				forwardIndex.setDocId(rs.getInt(2));
				forwardIndex.setWord(rs.getString(3));
				forwardIndex.setNhits(rs.getInt(4));
				forwardIndex.setHitlist(rs.getString(5));
				forwardIndex.setTermfre(rs.getDouble(6));
			}
			
			if(cnt == 0)
				return null;
			
		}
		catch(Exception e) {
			
			System.out.println("get failure !");
			e.printStackTrace();
		}
		
		return forwardIndex;
	}