Load the file from the file system. Open the file in read/write mode. Read the line into a StringBuffer. Get the length of the string that you want to replace Replace the String using the StringBuffer replace(startindex, endindex, Stringtoreplace) method
With RandomAccess you can locate a string in a file and overwrite it with something else of exactly the same length. Since "failure" and "success" both have 7 letters you could do it in place. The "locate" part might be a little challenging, though, since there's no API to read one line at a time from RandomAccess.
With ordinary file io you can read the input one line at a time, examine each line, make the change when you find the target, and write a new file one line at a time. I like this trick to be very safe when rewriting a file:
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi