I want to know what is the difference between while(rs.next()) and if(rs.next())? I'm not sure about this but I think that while is for more than 1 data in the db while if is to check whether there is data or not inside db and can only retrieve 1 data. so my question is: if I have no data on 1 thing but I have 1 or more data on another 1 then how to check for that one.because in my program some still don't have data so this part, I always have java.lang.nullpointerexception. thanks...
The next() method of a ResultSet moves the cursor on to the next record, returning true if there is another record to move to and false if there is not. Typically since you don't usually know how many records are in a ResultSet you would access its contents in a loop, so:
is the typical way of dealing with ResultSets. I suppose you could use:
if you are sure there will always be 0 or 1 records. But it sounds like a dangerous assumption.