TableColumnModel columnModel = header.getColumnModel();
for (int column = 0; column < columnModel.getColumnCount(); column++) {
TableColumn aColumn = columnModel.getColumn(column);
TableCellRenderer renderer = aColumn.getHeaderRenderer();
if (renderer == null) {
renderer = new DefaultRenderer();
}
Component comp = renderer.getTableCellRendererComponent(
header.getTable(), aColumn.getHeaderValue(), false, false, -1, column);
int cHeight = comp.getPreferredSize().height;
Enumeration enumer = ((GroupableTableHeader) header).getColumnGroups(aColumn);