DefaultTableModel model = new DefaultTableModel();
    JTable table = new JTable(model);
    
    // Create 2 columns
    model.addColumn("Col1");
    model.addColumn("Col2");
    
    // Change name of first visible column
    int vColIndex = 0;
    table.getColumnModel().getColumn(vColIndex).setHeaderValue("New Name");
    
    // Force the header to resize and repaint itself
    table.getTableHeader().resizeAndRepaint();