[katie]

if the content of the foo.txt file is a collection of ISO8859-1 characters:

Code:

BufferedReader br = new BufferedReader
(new InputStreamReader(new FileInputStream("foo.txt"), "ISO8859_1"));

Read them lines into an ArrayList. Then,

Code:

PrintWriter pw = new PrintWriter("foo.txt", "UTF8");

would overwrite the foo.txt with UTF-8 characters.