java中的JTable如何刷新

DefaultTableModel defaultTableModel=new DefaultTableModel();

    refreshButton1.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            defaultTableModel.setColumnIdentifiers(new Object[]{"mdseID","mdseName","mdseKinds","mdseBarcode","specification","mdseUnit","mdseState","CurrentStorage","lowestStorage","unitPrice","sellPrice","produceFactory"});
            String sql="select * from mdseinfo";
              ResultSet rs = DBHelper.query(sql);
                              try {
                                while(rs.next()){
                                    try {
                                        String mdseID=rs.getString("mdseID");
                                        String mdseName=rs.getString("mdseName");
                                        String mdseKinds=rs.getString("mdseKinds");
                                        String mdseBarcode=rs.getString("mdseBarcode");
                                        String specification=rs.getString("specification");
                                        String mdseUnit=rs.getString("mdseUnit");
                                        String mdseState=rs.getString("mdseState");
                                        float CurrentStorage=rs.getFloat("CurrentStorage");
                                        float lowestStorage=rs.getFloat("lowestStorage");
                                        float unitPrice=rs.getFloat("unitPrice");
                                        float sellPrice=rs.getFloat("sellPrice");
                                        String produceFactory=rs.getString("produceFactory");
                                        
                                        defaultTableModel.addRow(new Object[]{mdseID,mdseName,mdseKinds,mdseBarcode,specification,mdseUnit,mdseState,CurrentStorage,lowestStorage,unitPrice,sellPrice,produceFactory});
                                    } catch (SQLException e1) {
                                        // TODO Auto-generated catch block
                                        e1.printStackTrace();
                                    }
                                    
                                }
                            } catch (SQLException e1) {
                                // TODO Auto-generated catch block
                                e1.printStackTrace();
                            }
                          
            
        }
    });JTable tb=new JTable(defaultTableModel);

以上是我界面的表格，我一点刷新按钮就会显示和这个表格，但是我现在的问题是，每次刷新时候如何把之前刷新的表格内容给删除，然后出来新刷新的表内容（比如第一次按刷新后会出现这个表格，再刷新一次就又会在下面出现新的修改后的表格，我想把之前第一个表格删掉）

调用defaultTableModel.setRowCount(0);
就可以清空数据，然后加入新的数据