You can define which column are sortable by calling the method:

public void setSortableColumn(int column, boolean sortable);

All columns are sortable by default.

The non-sortable columns can be retrieved with:

public int[] getNonSortableColumns();

,which returns the non-sortable columns as an int array.

You can also determine if a column can be sorted by calling:

public boolean isSortable(int column);