The compute clause is meant to present summary information. That is why it is limited to one line.
I don't think there is a way to get all that information in standard SQL. You could do another query (using group by) to calculate the totals. However, it is easier and more efficient to just do the counting in Java. You are returning the department already. If there is more than one department with the same name, you can return the deptId too. Just count the number of records as you loop through the resultset.