public String topicsdelete() { String delTopicId = this.request.getParameter("topicid"); System.out.println("topicid=" + delTopicId); List<Comment> topiccomments = new ArrayList<Comment>(); if (delTopicId != null && delTopicId.length() > 0) { try { topiccomments = bm.loadCommentsByTopicId(Integer.parseInt(delTopicId)); } catch (NumberFormatException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } for (Comment comm : topiccomments) { System.out.println("$$$---" + comm.toString()); try { bm.delete(comm); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } } Topic deltopic = new Topic(); deltopic.setId(Integer.parseInt(delTopicId)); try { bm.delete(deltopic); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } } this.listAllTopics(); return "delete"; }