I need help regarding this statement ....
i do an query
select max(ID) as maxID from ID

and now i want to retrieve record ....

i use rs.next method
den i rs.getString(maxID)

but it return null

Not sure what as MaxID is for, I would only use select MaxID from ID.

If he leaves off the max() function he will get multiple rows back - I think the poster is interested in getting the single largest value of the ID field in the ID table.

I think you need quotes around the column name (though it really should have given you a compile error unless you happen to have a variable named maxID floating around)
rs.getString( "maxID" )

You might also be encountering case sensitivity from the database, it might have converted the title to all caps "MAXID" or all lower "maxid". I've done code for both Oracle and Sybase and they handle case sensitivity differently.