try this
public void setUpTableData() {
DefaultTableModel tableModel = (DefaultTableModel) jTable.getModel();
/**
* additional code.
**/
tableModel.setRowCount(0);
/**/
ArrayList<Contact> list = new ArrayList<Contact>();
if (!con.equals(""))
list = sql.getContactListsByGroup(con);
else
list = sql.getContactLists();
for (int i = 0; i < list.size(); i++) {
String[] data = new String[7];
data[0] = list.get(i).getName();
data[1] = list.get(i).getEmail();
data[2] = list.get(i).getPhone1();
data[3] = list.get(i).getPhone2();
data[4] = list.get(i).getGroup();
data[5] = list.get(i).getId();
tableModel.addRow(data);
}
jTable.setModel(tableModel);
/**
* additional code.
**/
tableModel.fireTableDataChanged();
/**/
}