java manipulate alphabet list

1String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";int indexOfLetterD = alphabet.indexOf("D");//indexOfLetterD equals 3

1String middle3 = (string.length() < 3) ? null : 
2              string.substring(string.length() / 2 - 1, string.length() / 2 + 2);

1String middle3 = (string.length < 3) ? null : string.substring(string.length / 2 - 1), string.length / 2 + 2);

1for (int i = 'A'; i <= 'Z'; i++)
2    for (fileName: fileNameList) {
3        if ((int)fileName.charAt(0) == i) {
4            AlphabetList.add((char)i);
5        }
6    }
7}