JTable & AbstractTableModel(Delete row problem)

Question

Hi!!
I have used AbstractTableModel in my JTable.In case of multiple rows, i want to delete rows from interface as well as from database. As removeRow method is absent in AbstractTableModel.so DefaultTableModel has been used by casting but CastClassException throws. Here is Partial code(tried in many ways).Plz help me to solve the problem.
void jButtonCancel_actionPerformed(ActionEvent e) {
try{
jTable1.setModel(myModel); //jtable is object of JTable and myModel is of Abstract TableModel           
DefaultTableModel model=((DefaultTableModel)jTable1.getModel());
int row=jTable1.getSelectedRow();
if(row>=0){
model.removeRow();
jTable1.revalidate();
model.fireTableDataChanged();
System.out.println("Rows Delete");
catch(Exception sq){
sq.printStackTrace();
sq.getMessage();

Answer 1

Hmm...
A bit of studying java awaits you.
Anyway.
Your class:
public class MyModel extends AbstractTableModel
  // Do various sorts of coding here
}Is not an instance of DefaultTableModel, so, if you try to cast your model to a DefaultTableModel it will throw an exception since the conversion is impossible.
Recomended solution:
Add a remove method for your class MyModel that does the following:
public void removeRow(int row)
  // data removed
  // fire removed data event
}Then instead of casting to DefaultTableModel, cast it to 'MyModel' and call the method 'removeRow'.
When it comes to inheritance and casting you can always cast an object to any of it's superclasses or any of the interfaces it supplies or it's superclasses suppplies. You can not cast an object to a instance of which it has no relation with.
In you example, your table model class extends the abstract table model but it does not extend the DefaultTableModel. An instance of your class can be casted to AbstractTableModel and so can an DefaultTableModel because they are both subclasses from AbstractTableModel. They can also be casted to TableModel since all of these implement the interface needed to fullfill TableModel's specification.
If you cast a DefaultTableModel instance to TableModel you can not try to cast it upwards to something the instance wasn't from the beginning.
Example:
DefaultTableModel dtm = new DefaultTableModel();
// When you do casting uppwards, there is no need for paranthesis
TableModel tm = dtm;
// You can easily later on cast this back to what is what or to any step
// in between
DefaultTableModel stillSameModel = (DefaultTableModel)tm;
// You can not however cast to something the instance never was
// Row below will cause an compile error:
JComboBox jb = (JComboBox)dtm;
// This since JComboBox can never be an superclass to the DefaultModel
// More dangerous errors that can't be catched until runtime is the
// one you made. Ie: I do what could be an valid cast
MyModel mm = (MyModel)tm;
// Since MyModel is an TableModel and tm refers to an TableModel,
// this casting is approved by the compiler.
// It will on the other hand throw an ClassCastException when run since
// the variable tm contains an instance of DefaultTableModel which
// is not an MyModel instance.Recomended that you read up on inheritance and basic OO.
Regards,
Peter Norell