Inserting a Row in to a JTable

Question

I have been looking and looking in the tutorials and other topics but can not find exactly what I need. I just need to start with a blank table and once something happens it will trigger to insert a row in to the table for updates.
Here is the code on how I start the table.
1. Object[] columnNames = {"Type", "Date", "Time", "Computer"};
2. Object[][] rowData = {};
3. errorTable = new JTable(rowData, columnNames);
4. DefaultTableModel dtm = (DefaultTableModel)errorTable.getModel();
5. dtm.setDataVector(rowData, columnNames);
I get a ClassCastException on line 4.....why is that???

Answer 1

Okay, so that worked to use DefaultTableModel.....but when i try and insert a row later on I get a null pointer exception when hitting line 7 below:
//Getting computer name from the tree node
1. String computer = getName(((DefaultMutableTreeNode) serverTree.getLastSelectedPathComponent )).getParent().toString(), "/");
//Adding information to a vector to add to table
2. dataVector.addElement("Information");
3. dataVector.addElement("");
4. dataVector.addElement("");
5. dataVector.addElement(computer);
6. holdVector.addElement(dataVector);
//Hoping to insert the row here (but get null pointer)
7. errorTableModel.setDataVector(dataVector, holdVector);
What is the issue??? Do I need to do an insert row now or what? Thank you in advance.