Question: Repeat Exercise, but add code that detects if a file is referenced more than once. When such a situation is detected, the additional references are ignored.
Exercise: Suppose a data file contains lines that consist of either a single integer, or the name of a file that contains more lines. Note that a data file may reference several other files and the referenced files may themselves contain some additional file names, and so forth. Write a method that reads a specified file and returns the sum of all the integers in the file and any files that are referenced. You may assume that no file is referenced more than once.