ClassCastException when using DefaultTableModel.getValueAt to get data

Question

Hi,
I'm using JTable to display,add and edit customers informantion in my project, the properties of each customer is displayed in corresponding cloumns in one row. The properies consist of id(Integer), name(String)...etc, it works fine when I set and get the properties of existing customer information into the DefaultJTableModel(dm for short) of the table I created, but when I added the new row using dm.addRow() and get the information typed in manually, an exception of ClassCastException was raised
here is the way I created JTable columns,and added a new row
DefaultJTableModel md =(DefaultJTableModel ) this.jTable.getModel();
md.addColumn("ID");
md.addColumn("Name");
md.addRow(new Object[]{
Integer.valueOf("1"),
"A"
} )then I captured mousecliked event of an Add button to add a new row in the table as bellow
md.addRow(new Object[]{null}) // as there's no need to initialize each column of each new row ,i used null instead of new Object[]{default id, default name};after editing the new row added to the table I captured the mouse cliked event of an Save button to save the added row which I wanted to write back to an bean
Customer c=new Customer()
c.setId((Integer)md.getValueAt(0,0));
c.setName((String)md.getValueAt(0,1));
c=new Customer()
c.setId((Integer)md.getValueAt(1,0)); // here is the point which caused the ClassCastExcption happened
c.setName((String)md.getValueAt(1,1));the exception message is
java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
It seems the newRow() method set all the columns of a new row to the type of String,
my question is how can I set the data type of a column in the table?

Answer 1

When you edit a table cell, JTable writes your edit back into the model. Most of the time, editing means entering text, so obviously, JTable will write a String into your model. JTable might be able to handle simple conversions such as String to Integer, but at the very least you would have to tell the table that you want only Integers in your column by implementing [TableModel.getColumnClass|http://java.sun.com/javase/6/docs/api/javax/swing/table/TableModel.html#getColumnClass(int)] appropriately. I honestly don't remember if the table can do this, though. If it can't, you probably need to either use a custom editor that converts the user entered text into an appropriate object or you need to use a custom model that handles the conversion in its setValue method.