Then you've been lying to us, because you claim you wrote that code, yet the file from netbeans.org is the exact same except a) without all the extra line breaks, and b) with Created on 23 February 2006, 16:13 in the file's initial comment. You couldn't have written this code this week if the file says 2006.
George Sarbu wrote:The application work fine, but I want to add a button for make some calculations(e.g.: values_column A + values_Column B, and put the result in column C)
If it is NetBeans generated, then you can just drag the button from pallette on to the form (in 'Design' mode). However, to understand how the buttons are laid out, you would need to understand layouts. To perform an action on a button click (like add in your case), you need to write action listeners. You can read about actions here