How can I get the size of all lines or the last line number in a DB?

Question

I want to display a certain number of lines from a DB.
But before I fetch them out, I must know how many lines of this DB has.
I donnot know if there is some methods have this function. I know the last() method can move the cursor to the last line, but some DB cannot support this function.
Could someone know the answer or some examples about displaying data in a jsp?
Thanks a lot.

Answer 1

To get the number of rows in a ResultSet, loop over the result set with while(res.next()). Read each row into an object. Add each object into a, say, LinkedList. At the end, you will have the rows nicely converted to objects (which you probably should do anyway), and list.size() will give the number of objects.
There are other ways to get the number of objects, but list.size() is the easy and reliable way. If you don't need the rows converted to objects ...why did you select them in the first place?
Tricks with last() and whatnot sort of work. They read the entire result set into memory. But you'll need to write the while(res.next()) loop anyway. No point in having the computer do the same thing twice.