How To Add Row Names To JTable

I'm trying to implement a spreadsheet-like table using JTable and this is the basic structure.

String[] colnames={"A","B","C","D","E"};
String[][]data=new String[28][5];
sheet = new JTable(data,colnames);
//sheet.setBounds(10, 36, 527, 214);
JPanel tablepane=new JPanel();
tablepane.add(new JScrollPane(sheet));
tablepane.setSize(800, 400);

In a spreadsheet, alphabetical letters are column names and numbers represent rows. I have named the columns and I need to name the rows in the same way. Or if I am to set the first column in every row as row headers, how can I make then non-editable by the user? In addition to that, how can I make the table appear bigger? There's a lot of space but the table appears to be small.