Excel-like JTable Cell Editor, with an empty cell at edition start
public void propertyChange(PropertyChangeEvent e)
{
    //  A cell has started/stopped editing
    if ("tableCellEditor".equals(e.getPropertyName()))
    {
        if (table.isEditing())
            processEditingStarted();
        else
            processEditingStopped();
    }
}

private void processEditingStarted()
{
    SwingUtilities.invokeLater( this );
}

public void run()
{
    row = table.convertRowIndexToModel( table.getEditingRow() );
    column = table.convertColumnIndexToModel( table.getEditingColumn() );
    oldValue = table.getModel().getValueAt(row, column);
    newValue = null;

    table.getModel().setValueAt(null, row, column);
    table.updateUI();
}