Answer by kyxap for How to generate a random alpha-numeric string?

Also you can generate any lower or UPPER case Letters or even special chars thought data from ASCII table. For example, generate upper case letters from A (DEC 65) to Z (DEC 90):

String generateRandomStr(int min, int max, int size) {
    String result = "";
    for (int i = 0; i < size; i++) {
        result += String.valueOf((char)(new Random().nextInt((max - min) + 1) + min));
    }
    return result;
}

Generated output for generateRandomStr(65, 90, 100));:

TVLPFQJCYFXQDCQSLKUKKILKKHAUFYEXLUQFHDWNMRBIRRRWNXNNZQTINZPCTKLHGHVYWRKEOYNSOFPZBGEECFMCOKWHLHCEWLDZ