Hai Kate,
I guess
you should be successfull in setting the preferred column widths in JTable, yet you will not be seeing the scroll pane, since if we scroll some of the columns, the adjacent columns gets adjusted and fits within the viewport area, hence to have the HORIZONTAL SCROLL BAR always, set the minimum width for all the columns and set the setAutoResizeMode(0), you will get the scroll bar, especially for the table with more no. of columns.
table.setAutoResizeMode(0);
column = table.getColumnModel().getColumn(columnIndex);
column.setMinWidth(80);
after setting this, as usual you add the table to the scroll pane, you will get the horizontal sliding successfully.
if possible, let me know your result..
Have a great day.
-sakthi.