public class Crypt {

    private static final String alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-";
    private String result = "";
    private static final int base = alphabet.length();

    public String encode(int number) {
        char[] alphabetArray = alphabet.toCharArray();
        if (number == 0) {
            String temp = "";
            temp += alphabet.charAt(0);
            return temp;
        }

        while (number > 0) {
            result += alphabetArray[number % base];
            number = (int) Math.floor(number / base);
        }
        return reverse(result);
    }

    private String reverse(String inputString) {
        String temp = "";
        for (int i = inputString.length() - 1; i >= 0; i--) {
            temp += inputString.charAt(i);
        }
        return temp;
    }
}