任意进制、自定义字符表的数字表示方式转换工具

AlphabetEncoder.java

public final class AlphabetEncoder {
    private static final String[]             ALPHABET      = { "0", "1", "2", "3", "4", "5", "6",
                                                                "7", "8", "9", "成", "都", "欢", "迎",
                                                                "你", "们" };

    private static final long                 ENCODE_LENGTH = ALPHABET.length;

    private static final Map<String, Integer> idxMap        = new HashMap<>();
    static {
        for (int i = 0; i < ALPHABET.length; i++)
            idxMap.put(ALPHABET[i], i);
    }

    public static String encode(long num) {
        final List<String> list = new ArrayList<>();

        do {
            list.add(ALPHABET[(int) (num % ENCODE_LENGTH)]);
            num /= ENCODE_LENGTH;
        } while (num > 0);

        Collections.reverse(list);
        return String.join("", list);
    }

    public static long decode(final String encoded) {
        long ret = 0;
        String c;
        for (int index = 0; index < encoded.length(); index++) {
            c = encoded.substring(index, index + 1);
            ret *= ENCODE_LENGTH;
            ret += idxMap.get(c);
        }
        return ret;
    }

    public static void main(String... args) {
        long n = 3137331;
        System.out.println(Long.toHexString(n));
        System.out.println(encode(n));
        System.out.println(decode(encode(n)));
    }
}